Glossary - All Terms and Definitions Listed Alphabetically


A single-wire (plus ground) communications protocol.

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1-Wire Master A 1-Wire interface master controller.
10GbE 10-Gigabit Ethernet
3G Third-generation mobile telephone protocols that support higher data rates, for non-voice communications such as multimedia and Internet access.
3GPP Third Generation Partnership Project, a collaboration of cell phone technology standards bodies.
802.11 IEEE standard that specifies medium-access and physical-layer specifications for 1Mbps and 2Mbps wireless connectivity between fixed, portable, and moving stations within a local area.
802.11a The IEEE standard that governs the deployment of 5GHz OFDM systems. It specifies the implementation of the physical layer for wireless UNII b.
802.11b An international IEEE standard for WLAN networks, operating at 2.4GHz and providing a maximum data transfer rate of 11Mbps.
802.11g A proposed standard that describes a wireless networking method for a WLAN that operates in the 2.4GHz radio band (ISM: Industrial Scientific Medical frequency band). It transfers data at up to 54Mbps.

A-weighting is a standard weighting curve applied to audio measurements, designed to reflect the response of the human ear.

Sound-pressure levels derived using A-weighting are denoted by "dBA," or A-weighted dB levels.

A/D Converter Analog to digital. Specifically: A/D converter, a circuit that converts analog signals into a stream of digital data.

An accelerometer is a sensor used to measure acceleration. Acceleration is defined as the rate of change of velocity i.e. how quickly a body is speeding up or slowing down while travelling in a given direction.

Physically, an accelerometer is a microelectromechanical (MEMS) device which is machined using microfabrication technology. Accelerometers are fabricated in a multilayer wafer process, measuring acceleration forces by detecting the displacement of a mass relative to fixed electrodes.

How does an accelerometer work?

Capacitance is commonly used as a sensing approach in accelerometers. This works on the principle that acceleration is related to the change in the capacitance of a moving mass (Figure 1). This accelerometer sensing technique is known for its high accuracy, stability, low power dissipation and simpler construction. It is not prone to noise and variation with temperature. The bandwidth of a capacitive accelerometer is only a few hundred Hertz because of its physical geometry (spring and air trapped inside the IC which acts as a damper).

moving mass creating variable capacitance

Figure 1. A moving mass creating variable capacitance

The capacitance sensing structure can be either single-sided or a differential pair (a movable mass on either side of the fixed electrode).

Since the change in capacitance for a single mass/electrode pair is tiny, multiple movable and fixed electrodes are connected together in a parallel configuration. This creates a much greater change in capacitance, which is detected more easily and increases accuracy of measurement.

The signal from the capacitance sensing structure then undergoes charge amplification, signal conditioning, demodulation, and lowpass filtering before being converted into a digital domain using a sigma-delta ADC. The serial digital bit stream from the ADC is then sent to a host controller (using an appropriate protocol like SPI or I2C) for further processing.

A shock sensor is a type of accelerometer that can detect high acceleration and deceleration.

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Advanced Configuration and Power Interface (ACPI) is an industry-standard specification (co-developed by Hewlett-Packard, Intel, Microsoft, Phoenix, and Toshiba) for operating-system-directed power management for laptop, desktop, and server computers. A replacement for APM.

ACPR Adjacent (alternate)-channel power ratio
ACR Accumulated current register

What does ADAS stand for?

ADAS stands for Advanced Driver Assistance Systems.

What is ADAS?

ADAS automotive display

The list of ADAS features is extensive and includes driver monitoring systems (DMS) to monitor a driver’s attention level, autonomous driving, adaptive front lighting control, automatic parking, traffic sign recognition and more. New ADAS technologies have the potential to improve driver safety and comfort, and even more importantly, to reduce automobile accidents and casualties. However, the adoption of ADAS technologies introduces new issues for automotive design especially in electronic solution size, safety, and reliability.

Why is ADAS important?

ADAS is a key disruptive technology ushering in a new age of smart mobility in transportation. Automakers increasingly see themselves as both product manufacturers and mobility service companies. In addition to developing next-generation connected and autonomous vehicles that will improve traffic flow and safety, automakers are investing in a wide swath of new mobility services. Urban planners will use the mobility ecosystem to reduce congestion, while generating related benefits such as fewer traffic accidents, better air quality, and a smaller urban footprint for parking. ADAS, with its emphasis on safety, is even expected to disrupt the automobile insurance industry to the benefit of consumers.

What are the key enablers for ADAS?

ADAS capabilities are enabled by a plethora of sensors deployed across the car which are networked to I/O modules, actuators, and controllers throughout the automobile. Ultimately, the on-board sensors connected to cloud support functions will provide external data from other vehicles and from cloud infrastructure for connected safety, advanced driver assistance support, and autonomous driving software and functions.

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See Also: LiDAR


An analog-to-digital converter (also known as an ADC or an A/D converter) is an electronic circuit that measures a real-world signal (such as temperature, pressure, acceleration, and speed) and converts it to a digital representation of the signal.

How does an ADC work?

An ADC compares samples of the analog input voltage (produced using a Sample and Hold circuit) to a known reference voltage and then produces a digital representation of this analog input. The output of an ADC is a digital binary code.

By its nature, an ADC introduces a quantization error, which is simply the information that is lost. This error occurs because there are an infinite number of voltages for a continuous analog signal, but only a finite number of ADC digital codes. Therefore, the more digital codes that the ADC can resolve, the more resolution it has, and the less information lost to quantization error.

In A/D conversion, the Nyquist principle (derived from the Nyquist-Shannon sampling theorem) states that the sampling must be at least twice the maximum bandwidth of the analog signal being converted, in order to allow the signal to be accurately reproduced. The maximum bandwidth of the signal (half the sampling rate) is commonly called the Nyquist frequency (or Shannon sampling frequency). In real life, sampling rate must be higher than that (because filters used to re-produce the original signal are not perfect). As an example, the bandwidth of a standard audio CD is a bit less than the theoretical maximum of 22.05kHz (based on the sample rate of 44.1kHz).

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ADM Add/Drop Multiplexer: A synchronous transmission network (SDH or Sonet) can carry multiple channels. An Add/Drop Multiplexer is a device that adds (inserts) or drops (removes) lower-data-rate channel traffic from the higher-rate aggregated channel.
ADPCM Adaptive Differential Pulse Code Modulation: A compression technique that encodes only the difference between sequential samples.
ADS Analog design system
ADSL Asymmetric Digital Subscriber Line: A method for moving data over regular phone lines. An ADSL circuit carries much more data than a modem can encode on a regular phone connection. ADSL rides on the regular phone wires coming into the subscriber's premises (twisted pair copper).
AEC-Q100 A qualification test sequence for integrated circuits developed by the AIAG automotive organization.

Analog Front End: The analog portion of a circuit which precedes A/D conversion.

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AGC Automatic Gain Control: A circuit that modulates an amplifier's gain, in response to the relative strength of the input signal, in order to maintain the output power.
Ah Ampere-hour(s): A measure of battery capacity. A 4Ah battery could, for instance, deliver 1A for 4 hours, 1/2A for 8 hours, etc.
Air Discharge

Air discharge is a method for testing ESD-protection structures in which the ESD generator is discharged through an air gap between the generator and the device under test (DUT).

See Also: Human Body Model

AIS Alarm indication system
AISG The Antenna Interface Standards Group (AISG) creates open specifications for antenna-line control and monitoring for 3G systems.

Source: AISG website


In A/D conversion, the Nyquist principle states that the sampling rate must be at least twice the maximum bandwidth of the analog signal. If the sampling rate is insufficient, then higher-frequency components are "undersampled" and appear shifted to lower-frequencies. These frequency-shifted components are called aliases.

The frequencies that shift are sometimes called "folded" frequencies because a spectral plot looks like it was folded to superimpose the higher frequency components over the sub-Nyquist portion of the band.

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An alternator is an electromechanical device that converts mechanical power into AC electrical power.

Typically, a magnet spins inside a coil, inducing alternating current in the windings. The magnet can be a permanent magnet, an iron rotor in which a magnetic field is induced, or an electromagnet powered by an externally applied current.

See Also: Generator


Amplitude Modulation (AM) is a modulation method in which the carrier amplitude changes with the input signal amplitude.

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Ambient Temperature

Ambient temperature is the temperature of the air surrounding a component.

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Ambient Temperature Sensor

An ambient temperature sensor is a sensor used to measure the temperature of the air that surrounds a component (the ambient temperature).

Learn More: Temperature Sensor ICs

AMLCD Active-matrix liquid-crystal display
Amp 1. Ampere

2. Amplifier


Ampacity is the amount of current a conductor can carry without exceeding its specified temperature, in amperes.


Ampere(s), the unit of electrical current. Current is defined as the amount of charge that flows past a given point, per unit of time.

The symbol I is used for current in equations and A is the abbreviation for ampere.


A measure of charge (or current flow over time).

  • One ampere-hour (or amp-hour or Ah) is a current of one ampere flowing for one hour. The amount of charge transferred in that hour is 3,600 coulombs (ampere-seconds).
  • A milliampere-hour (mAh or milliamp-hour) is a thousandth of an amp-hour.
  • An ampere-second (A-s or amp-second) is an amp supplied for one second.

A common use of the term is rating energy storage device capacity, especially rechargeable batteries. For example, a 12-volt, 7Ah rechargeable battery used in an alarm system will supply an amp at the rated voltage range for seven hours, 2 amps for 3.5 hours, etc. If my alarm consumes 250mA, this battery would operate the system for 28 hours.

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An electrical or electronic amplifier is a circuit that uses an external power supply to generate an output signal that is a larger replica of its input.

An audio amplifier (an easily recognizable application) is used to increase the volume of a speaker’s voice so they can be heard more easily in large areas. While voltage is the most commonly amplified type of input signal, amplifiers can also be designed to increase current. An amplifier that increases output current drive is called a power amplifier.

Most amplifiers perform linear amplification, but some are logarithmic in nature. In a circuit diagram, an amplifier is usually represented by a triangle.

amplifier circuit diagram

The formula for a voltage amplifier with Gain A is:

Vout = A * Vin

Amplifiers are classified by linearity and efficiency. A class A amplifier is the most linear (but least efficient) type of amplifier. Other common amplifier classes include B, AB, C and D in order of decreasing linearity and increasing efficiency.

Apart from high gain an electronic amplifier circuit should have the following characteristics:

  • Very high input resistance (ideally infinite)
  • Very low output resistance (ideally zero)
  • Very little delay (ideally none)

Amplification can be done relative to ground (single-ended) or relative to another terminal (differential). The “operational amplifier", commonly referred to as an op-amp is a special type of differential amplifier which has extremely high (theoretically infinite) gain. This allows it to be used in a negative feedback configuration with other electronic components (resistors, capacitors, inductors) to perform mathematical operations (hence ‘operational’). Apart from amplification, the op-amp can be configured to perform attenuation (lower output voltage), addition, subtraction, differentiation and integration.

Learn More: Amplifier products

Amplifier Class

Amplifier circuit types are divided into "classes" which describe whether the amplifier operates in a linear or switching mode, and any techniques used to restore linearity of output.

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AMPS Advanced Mobile Phone System: An analog only, 1G standard that operates in the 800MHz to 900MHz frequency band. It is still widely used in the United States.
AMR Automatic Meter Reading: A system installed to read a utility meter remotely.

A system in which an electrical value (usually voltage or current, but sometimes frequency, phase, etc.) represents something in the physical world.

The electrical signal can then be processed, transmitted, amplified, and finally, transformed back into a physical quality.

For example: A microphone produces a current that is proportional to sound pressure. Various stages amplify, process, modulate, etc. Ultimately, a varying voltage is presented to a speaker which converts it back to sound waves.

By contrast, a digital system handles a signal as a stream of numbers.

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Analog Switch

An analog switch (sometimes just called a "switch") is a switching device capable of switching or routing analog signals (meaning signals that can have any level within a specified legal range), based on the level of a digital control signal.

Commonly implemented using a "transmission gate," an analog switch performs a function similar to that of a relay.

Analog switch schematic diagram Analog switch circuit symbol

Transmission gate schematic diagram (left) and circuit symbol (right).

For example, an analog switch can turn an audio signal on or off based on a MUTE signal; or analog switches could send one of two signals to a headphone amplifier.

Most commonly implemented using CMOS technology integrated circuits. Maxim makes hundreds of examples.

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Analog Temperature Sensor

An analog temperature sensor is a temperature sensor with a continuous analog voltage or current output that is related, usually linearly, to the measured temperature.

Learn More: Temperature Sensor ICs


Combining two signals so that the output is on if both signals are present. This can be accomplished by an AND logic gate (two inputs, one output which is high if both inputs are).

Learn More: Logic Gates

ANSI American National Standards Institute

An anti-aliasing filter is used before A/D conversion. It is a lowpass filter that removes signal components above the Nyquist frequency, thereby eliminating their sampled replicas (aliases) in the baseband.

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APC Automatic Power Control: Feature in laser drivers (such as the MAX3669) that uses feedback from the laser to adjust the drive, to keep the laser's output constant.

An avalanche photodiode (APD) is a photodiode designed to take advantage of avalanche multiplication of photocurrent to provide gain.

As the reverse-bias voltage approaches the break-down voltage, hole-electron pairs created by absorbed photons acquire sufficient energy to create additional hole-electron pairs when they collide with ions. Thus a multiplication or signal gain is achieved.

Learn More: Low-Noise APD Bias Circuit

API Application program interface: A software layer that allows a system to be programmed via a defined set of commands.

Advanced Power Management (APM) is a power management standard for computers that provides five power states: Ready, Stand-by, Suspended, Hibernation, Off.

See Also: ACPI

APON ATM (-based) passive optical network
APQP Advanced Product Quality Planning. System developed by the AIAG automotive organization to communicate common product quality planning and control plan guidelines for suppliers to the automotive industry.
ASCII American Standard Codes for Information Interchange

Application-specific integrated circuit.

Learn More: Maxim ASIC services


Automatic test equipment; automated test equipment.

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ATM Asynchronous transfer mode
Auto Shutdown

Auto Shutdown is a feature in EIA-232 interface devices which puts the IC into a low-power shutdown mode when no signal is present on the EIA-232 bus.

Learn More: RS-232 Features Explained

Autoshutdown Plus

Autoshutdown Plus is a feature in EIA-232 interface devices which puts the IC into a low-power shutdown mode when no signal is present on the bus or the transmitter inputs.

Learn More: RS-232 Features Explained


An autotransformer is a transformer that uses a common winding for both the primary and secondary windings. Essentially an inductor with a center-tap, an autotransformer is often used in power-supply boost-converter applications to achieve a higher output voltage, while limiting the peak flyback voltage seen by the power switch.

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AWG 1. Arbitrary waveform generator

2. American Wire Gauge: A measure of wire thickness (which also dictates cross-sectional area, and for a given material, ampacity). Example: 24 AWG wire has a nominal diameter of 0.0201in or 0.511mm. Also called the Brown and Sharpe Wire Gauge.

Note that steel wire is measured by a different gauge. AWG only applies to wire used to conduct electricity.

1. Bel: Measurement of a signal's power compared to a reference; also, measurement of sound pressure. See the more commonly used term, "decibel," or, "dB."

2. Symbol for magnetic flux density or magnetic field, as in "B-field."

Backup Step-Up Step-up, switching-regulator power supply with a backup battery switchover.

1. Bandwidth (BW) is a range of frequencies, or information, that a circuit can handle or the range of frequencies that a signal contains or occupies.

Example: An AM broadcast radio channel in the US has a bandwidth of 10kHz, meaning that it occupies a 10kHz-wide band, such as the frequencies from 760kHz to 770kHz.

2. The amount of data a digital channel or line can handle, expressed in bits per second (bps), kilobits per second (kbps), baud, or a similar measure.

Base Station

A base station (or basestation) is a wireless transceiver at a fixed location (e.g. atop a telephone pole) which is part of a wireless communications network, e.g. the cell phone network.

Typically, the base station connects to any cell phones in its area and relays the calls to the wired network.

A femto base station is a smaller, personal base station which might cover a home or building and connect via a DSL Internet connection.

Baseline The electrical signal from a sensor when no measured variable is present. Often referred to the output at no-load condition.
Bass Boost Circuitry that boosts the bass response of the amplifier, improving audio reproduction, especially when using inexpensive headphones.
Battery Backup A feature of microprocessor supervisory circuits and some power supplies to switch between a main power source and a battery.
Battery Freshness Seal A feature in microprocessor supervisory circuits which disconnects a backup battery from any down-stream circuitry until VCC is applied the first time. This keeps a backup battery from discharging until the first time a board is plugged in and used, and thus preserves the battery life.
Battery Fuel Gauge

A battery fuel gauge (also called a battery gas gauge) is a feature or device that measures the accumulated energy added to and removed from a battery, allowing accurate estimates of battery charge level.

How do you use a battery fuel gauge?

Battery systems may be designed with a host-side fuel gauge, or a pack-side fuel gauge.

Host-side battery fuel gauge implementation

A host-side fuel gauge resides on the host system and is connected to the application processor, as shown above. Having the fuel gauge as part of the application circuit instead of being located inside the battery makes the battery cheaper and easier to replace.

Pack-side battery fuel gauge implementation

A pack-side fuel gauge resides on the battery pack and is connected to the cell, as shown above. The proximity of the cell to the fuel gauge has advantages including improved accuracy of state of charge reporting and tiny solution size.

How do fuel gauges work?

There are two main methods of battery fuel gauging: coulomb counting and measuring open circuit voltage (OCV).

Coulomb counting is the process of estimating the amount of charge used by measuring the charge going into and coming out of the battery. While this works well in the short-term, a small drift error increases continuously over time and the battery needs to reach full and empty periodically in order to correct these errors.

Another way to monitor the state of charge (SOC) of a battery is to measure the open circuit voltage. OCV is estimated by measuring the immediate voltage and by running a real-time simulation of the battery model using battery characterization and past voltage history. Because OCV is reliably related to a battery’s SOC, the former can be used to determine the latter. This method is more accurate because it does not suffer from capacity drift over time and uses less power because it does not require a current sense resistor.

Coulomb counting offers better short-term accuracy, while OCV is better for long-term. To provide better results over a wider range of applications, these two methods can be combined with algorithms such as ModelGauge, which uses the OCV algorithm to periodically remove the offset error introduced by the coulomb counter while maintaining the stability of a voltage-based fuel gauge.

The type of battery fuel gauge you’ll want to use will depend on your application.

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Battery Monitor

A feature that monitors the voltage on a battery and indicates when the battery is low. It is usually implemented using a comparator to compare the battery voltage to a specified level. May also include functions such as charging, remaining capacity estimation, safety monitoring, unique ID, temperature measurement, and nonvolatile (NV) parametric storage.

Learn More: Battery Monitors, Protectors, and Selectors

Battery Switchover A circuit that switches between the higher of a main supply and a backup battery.
BCD Binary-coded decimal (BCD) is a representation of a number in which each decimal digit (0-9) is encoded in binary, with four bits per decimal digit.

Bit Error Rate (BER) is a measure of the number of erroneous bits which can be expected in a specified number of bits in a serial stream.

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A Bit Error Rate Tester (BERT) is a piece of test equipment which determines the bit error rate for a device under test (DUT).

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Beyond-the-Rails is Maxim's name for a feature of an IC that can process inputs and provide output voltages that exceed the supply rails. The feature is achieved through on-chip integration of necessary supply rails.

Learn More: Beyond-the-Rails Technology


Ball grid array: A packaging technology.

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Bidirectional means that the device accommodates signals traveling either direction though a single channel.

Bipolar Inputs An input which accommodates signals both above and below ground.
Bipolar Junction Transistor

A Bipolar Junction Transistor, or BJT, is a solid-state device in which the current flow between two terminals (the collector and the emitter) is controlled by the amount of current that flows through a third terminal (the base).

Contrast to the other main transistor type, the FET, in which the ouput current is controlled by input voltage (rather than by input current).


Built-in self-test.

Bit Banging A technique which uses the general-purpose ports of a microcontroller to emulate a serial interface standard (I2C, SPI, etc).
Bit Error Ratio

Bit error ratio is the number of erroneous bits divided by the total number of bits transmitted, received, or processed over some stipulated period.

See Also: Bit Error Rate

Blade Server

A blade server is a computer system on a motherboard, which includes processor(s), memory, a network connection, and sometimes storage. The blade idea is intended to address the needs of large-scale computing centers to reduce space requirements for application servers and lower costs.

Blink Control

Controls the display segment blink rate.

BLM Ball limiting metal

A technology that allows voice and data connections between a wide range of mobile and stationary devices through short-range digital two-way radio. For instance, it specifies how mobile phones, Wireless Information Devices (WIDs), computers and PDAs interconnect with each other, with computers, and with office or home phones.

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BLVDS Bus low-voltage differential signal
BOC Bit-oriented code
Boost Converter A power supply that steps an input voltage up (boosts it) to a higher, regulated voltage.
Bootstrap Often refers to using the output of a step-up converter to drive the main power FET switch, providing more gate drive than the input can supply alone. Also refers to using a switched capacitor to boost the voltage of a node.
BPON Broadband passive optical network

Binary phase-shift keying

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BRD Band-rate divisor

Break-Before-Make: A switch that is configured to break (open) the first set of contacts before engaging (closing) the new contacts. This prevents the momentary connection of the old and new signal paths.

Applies to mechanical systems (e.g. that use relays or manual switches) and to solid-state analog multiplexers and switches.

Learn More: Switches and Multiplexers


Bit-rate interface

Bridge Battery A battery intended to provide power to system memory while the main battery is replaced.
Bridge-Tied Load

Used in audio applications, the load (a speaker in this case) is connected between two audio amplifier outputs (it "bridges" the two output terminals).

This can double the voltage swing at the speaker, compared to a speaker that is connected to ground. The ground-tied speaker can have a swing from zero to the amplifier's supply voltage. A BTL-driven speaker can see twice this swing because the amplifier can drive either the + terminal of the speaker or the — terminal, effectively doubling the voltage swing.

Since twice the voltage means four times the power, this is a major improvement, especially in applications where battery size dictates a lower supply voltage — e.g. automotive or handheld applications.

Learn More: Optimizing Audio Bridge-Tied Load Amplifiers


Although the terms "brightness" and "luminance" are often used interchangeably, they are different. Luminance is the light intensity; brightness is how it is perceived by the human eye.

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Broadband A transmission medium with enough bandwidth to carry multiple voice, video, or data channels simultaneously.

This technique is used, for example, to provide fifty CATV channels on one coaxial cable; or to provide Internet access over cable TV; or to add DSL to a voice-grade telephone line.

A common technique is frequency-division. Each channel is modulated to a different frequency band and combined in the transmission medium. It is demodulated to its original frequency at the receiving end. Channels are separated by guardbands (empty spaces) to ensure that each channel will not interfere with its neighboring channels.


Brownout is a condition where the voltage supplied to the system falls below the specified operating range, but above 0V.


BSC (Basic Spacing between Centers) is a term that appears on IC package drawings in reference to dimensions between pins.

"Basic" spacing is nominal and can change with conditions. For example, the distance between the rows of pins on a DIP (dual inline package) is BSC because it changes when the auto insertion machine grabs the part, and again when the part is inserted. The BSC dimension, in this case, is the dimension of the hole spacing that the part will fit into, rather than the dimensions of the part itself.

Learn More: Package Materials

See Also: REF


Best-straight-line fit


Butterworth (filter)

BTS Base Transceiver Station: The stationary component of a cellphone system includes transmit-receive units and one or more antennae. The combined systems (often including multiple co-located systems and ganged directional antennae) is called a cell-site, a base station, or a base transceiver station (BTS).

A "buck" or "step-down" switch-mode voltage regulator is one in which the output voltage is lower than its input voltage.

Note: A customer asked the origin of the term and no one seems to know! A buck regulator is a step-down regulator, as opposed to boost. We think it's an American term — in England it was always "step-down."

Buck means to resist or reduce (as in "buck the trend"), and hence was used to denote a step-down. Conveniently, it alliterates with the opposite, a boost regulator.

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Buck-Boost Converter

What is a Buck-Boost Converter?

A buck-boost DC-DC converter (Figure 1), also called a buck-boost regulator, is an electrical or electronic circuit that is one of the three most commonly used DC-DC switching regulator topologies. A buck-boost converter produces a DC output voltage that can be either bigger or smaller in magnitude than its DC input voltage. As its name suggests, it combines the functions of a buck converter (used for DC voltage step-down) and a boost converter (used for DC voltage step-up).

simplified buck boost converter circuit

Figure 1. Simplified buck-boost converter circuit

What is a buck-boost converter used for?

A buck-boost converter is commonly used to create a constant DC output voltage from a variable DC input voltage source.

Where are buck-boost converters used?

Buck-boost converters are commonly used in mobile phones. The source of power in a mobile phone is a rechargeable battery which gradually discharges as the phone is used. This causes the battery voltage to slowly fall. If the battery were connected directly to the electronic circuits in the phone, the performance of the phone would vary as the battery voltage fell (the screen would get darker and the microphone volume would become lower). To prevent this happening, a buck-boost converter is used to provide a constant voltage to the phone’s electronic circuits, regardless of the battery voltage. For example, the voltage of a fully charged typical lithium-ion battery might be 3.8V. This might gradually fall to 2.8V as the battery discharges. By placing a buck-boost converter between the battery and the electronics, a stable voltage of 3.3V could be used to power the electronic circuits, meaning the performance of the phone would not degrade as the battery voltage fell, until it fully discharged, at which point the phone would power off.

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Burst Dimming

Burst Dimming is a method of controlling the brightness of cold cathode fluorescent lamps (CCFL) by turning the lamps on and off at a rate faster than the human eye can detect.

The on/off rate is nominally 100Hz to 300Hz. The higher the ratio of on-time to off-time, the brighter the lamps will be. Because of CCFL response times, on-time to off-time ratios of less than 1% are not practical.

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Burst Mode

1) A temporary high-speed data-transfer mode that can transfer data at significantly higher rates than would normally be achieved with nonburst technology.

2) The maximum short-term throughput which a device is capable of transferring data.

Bus Data path that connects to a number of devices. A typical example is the bus a computer's circuit board or backplane. Memory, processor, and I/O devices may all share the bus to send data from one to another. A bus acts as a shared highway and is in lieu of the many devoted connections it would take to hook every device to every other device.

Often misspelled "buss."


Bandwidth, Large Signal


Bandwidth, Small Signal


1. Capacitance, capacitor

2. Coulomb

3. Color portion of a video signal (see "Y/C" definition)

C/N Carrier-to-noise
CA Common anode
CAD Computer-aided design
CAN Controller Area Network. The CAN protocol is an international standard defined by ISO 11898.

What is Capacitance?

Capacitance is the amount of charge that can be stored at a given voltage by an electrical component called a capacitor. The unit of capacitance is the Farad (F) and a 1F capacitor charged to 1V will hold one Coulomb of charge. A capacitor is a passive electronic component that consists of two conductive plates separated by an insulating material called a dielectric. A voltage applied to the plates creates an electric field across the dielectric, which causes the plates to accumulate a charge. The charge remains after the voltage source is removed, allowing energy to be stored until the capacitor is discharged (allowing the stored energy to perform work).

What are the factors that affect capacitance?

The size of the conductive plates and the permittivity of the insulating dielectric material determine capacitance.

What is the effect of capacitance?

The larger the capacitance of a capacitor, the longer it takes to charge and discharge. This means it takes more time for voltage to build up (charge) or fall (discharge). This makes capacitance useful for filtering out small voltage variations that last only a short length of time, i.e., high-frequency transients.

What is parasitic capacitance and why is it important in electronic circuits?

Unintended (parasitic) capacitance exists between any two conducting materials – the closer their proximity and size, the greater the value. This must be factored into the design of a circuit as it can affect the speed at which it operates. For example, a large transistor may allow faster switching, but its larger size means a larger parasitic capacitance exists between its terminals and this may slow the speed of the circuit driving it.

How is capacitance measured?

Capacitance is measured using a capacitance meter. A 1F capacitor would be quite big – the size of a small bottle. For this reason, capacitance values used in electronic circuits are in the microfarad to nanofarad range.

Learn more: How to build a DC-DC Power Supply - Tutorial

Capacitive Crosstalk

Capacitive crosstalk is a phenomenon where a signal on one line/trace is capacitively coupled to an adjacent line/trace.

Learn More: Effects of Digital Crosstalk in Data Converters


A capacitor is a passive electronic component that consists of two conductive plates separated by an insulating dielectric.

A voltage applied to the plates develops an electric field across the dielectric and causes the plates to accumulate a charge. When the voltage source is removed, the field and the charge remain until discharged, storing energy.

Capacitance (or C, measured in farads), dictates the amount of charge that can be stored at a given voltage (a one-farad capacitor charged to one volt will hold one Coulomb of charge).

CardBus 32-bit version of the PC card (formerly PCMCIA) standard
CAS Column-Address-Strobe: The signal that tells the DRAM to accept the given address as a column-address; used with RAS and a row-address to select a bit within the DRAM
CAT3 Category 3: Refers to Ethernet cabling that satisfies the criteria for the EIA/TIA-568 standard's Category 3, which allows data transfers up to 10Mbps.
CAT5 Category 5: Refers to Ethernet cabling that satisfies the criteria for the EIA/TIA-568 standard's Category 5, which allows data transfers up to 100Mbps.
CATV Originally "Community Antenna Television," a term which now refers to any community television system distributed by cable.
CBR Constant bit rate
CC/CV Charger Constant Current/Constant Voltage battery charger
CCCv Constant current/constant voltage
CCD Charge Coupled Device: One of the two main types of image sensors used in digital cameras. When a picture is taken, the CCD is struck by light coming through the camera's lens. Each of the thousands or millions of tiny pixels that make up the CCD convert this light into electrons. The accumulated charge at each pixel is measured, then converted to a digital value. This last step occurs outside the CCD, in an analog-to-digital converter (ADC).

Cold Cathode Fluorescent Lighting: Often used as a backlight for LCD displays.

Learn More: CCFL Characteristics

See Also:

CCFT Cold Cathode Fluorescent Tube: Often used as a backlight for LCD displays.
CCK Complementary code keying
CCM Continuous-conduction mode; crossconnect module
CDC Clock distribution circuit
CDD Clock Distribution Device or Clock Distribution Driver
CDMA Code Division Multiple Access: A digital cellular technology that uses spread-spectrum techniques. Unlike GSM and other competing systems that use TDMA, CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence.
CDR Clock/data recovery. Clock/data recovery is a function or circuit that extracts a clock signal from an incoming data stream.
CE Control Chip enable control
CH Chebyshev (filter)
Ch. to Ch. Skew (Ps Max) Channel-to-channel skew. A signal on one channel has a different phase than the same signal on another channel (delayed/skewed). This is measured in picoseconds, max.
Channel Associated Signaling Channel Associated Signaling (CAS): Some communications protocols include "signaling" functions along with data. Channel Associated Signaling protocols include signaling in the data channel (as opposed to a dedicated signaling channel).

Also called Robbed Bit Signaling.

Chans. Channels
Charge Injection A parameter pertinent to analog switches. As an analog switch turns on and off, a small amount of charge can be capacitively coupled (injected) from the digital control line to the analog signal path.
Charge Pump

A power supply which uses capacitors to store and transfer energy to the output, often stepping the voltage up or down. Charge is transferred from one capacitor to another under control of regulator and switching circuitry.

Maxim offers both regulated and non-regulated charge pumps, as well as ICs with on-board charge pumps to boost internal voltages.

Learn More:

Charge Termination Method Method the battery charger uses to determine when to terminate the charging cycle.
CHATEAU CHAnnelized T1 and E1 And Universal HDLC controller
Chip 1. Integrated circuit: A semiconductor device that combines multiple transistors and other components and interconnects on a single piece of semiconductor material.

2. Encoding element, in Direct-Sequence Spread Spectrum systems.

Chip-Enable Gating A feature in microprocessor supervisory circuits which prevents the writing of erroneous data when power falls outside of spec. When the main power-supply voltage is below the minimum safe-operating limit, the feature disconnects the chip-enable signal path from the host microprocessor or microcontroller.
Chrominance The color portion portion of a composite video signal. Forms a complete picture once combined with the luminance component.
CID Consecutive identical digit(s)
CIM Cable integrity monitor

A circuit is a closed loop through which current can travel. It is made up of individual components such as resistors, capacitors, transistors, and inductors. Components can be assembled on a breadboard, or entire integrated circuits (ICs) can be manufactured on a printed circuit board (PCB).

Symbols for common circuit elements

AC voltage source schematic symbol

AC Voltage Source

Battery cell schematic symbol

Battery Cell

Capacitor schematic symbol


Diode schematic symbol


Ground schematic symbol


Inductor schematic symbol


Resistor schematic symbol


Switch schematic symbol


Wire schematic symbol


What are the types of circuits?

Circuits can be divided into categories of series vs. parallel, closed vs. open or short, and DC vs. AC.

Series circuits and parallel circuits

Series circuits have equal current flowing through all components in the circuit. Adding resistors in series increases the total equivalent resistance following the equation Req=R1+R2+...+Rn. The supply voltage is equal to the sum of all individual voltage drops.

Circuit diagram of a series circuit

Circuit diagram of a series circuit. There is only one path for current to travel.

Parallel circuits have equal voltage across all components in the circuit. Adding resistors decreases the total equivalent resistance, following the equation 1/Req=1/R1+1/R2+...+1/Rn. The total current is equal to the sum of individual branches of current.

Circuit diagram of a parallel circuit

Circuit diagram of a parallel circuit. There are multiple paths for current to travel.

Closed circuits, open circuits, and short circuits

A closed circuit has a complete path between the positive and negative terminals of its power source. An open circuit has an incomplete path due to an open switch, burned out or broken component, a frayed wire, etc. A short circuit contains a pathway of (near) zero resistance, called a short, usually due to unintended contact between components. All current will flow through the short, causing the circuit to malfunction.

DC circuits and AC circuits

DC (direct current) circuits have current only flowing in one direction. AC (alternating current) circuits have a power source that periodically switches the direction of the current.

What is in a simple circuit?

A simple circuit has just the most basic components for a working circuit: a source of voltage, a path for current to travel, and a resistor. These cover the three values necessary to satisfy Ohm’s Law, V=IR (voltage=current x resistance).

Circuit Simulator

Circuit Simulator

A circuit simulator is a piece of software that emulates the behavior of a real hardware circuit before it is built. The circuit simulator can be used to verify that a hardware design is behaving correctly and producing the desired output signal for a specified set of inputs.

The reliability of the tool depends on the creation of accurate mathematical models that describe the behavior of the circuit components in multiple variable scenarios including component tolerances, temperature and supply voltage.

What Design Tools Does Maxim Have?

Our portfolio of design tools provides you with the assistance you need to simplify and shorten your design process. These design tools help in multiple tasks, from IC selection to circuit design, analysis, and validation to BOM delivery and PCB layout. These include advanced system and sub-system level integrated circuit design tools such as the EE-Sim® design and simulation environment and the OASIS offline simulator.

What Can These Circuit Simulation Tools Do?

These tools include a portfolio of power devices available to design and simulate. You can quickly recalculate compensation after component changes, set component derating values, and perform efficiency calculations. They provide the flexibility to simulate user defined line transients as well as AC and steady-state conditions for user defined line and load settings. Other useful features include the ability to compare two designs, create custom user plots and reports, while schematics, plots and bill-of-materials can be exported in multiple file formats. Additional resources can be found in the form of product selectors, online calculators, SPICE models, IBIS models and CAD files.

Learn MoreDesign Tools

CISC Complex instruction set computer (CISC): Computer hardware designed to support complex instructions, as opposed to RISC (reduced instruction set computer) architecture.
Class A

The simplest type of amplifier, class A amplifiers are those in which the output transistors conduct (i.e. do not fully turn off) irrespective of the output signal waveform.

This type of amplifier is typically associated with high linearity but low efficiency.

See Also: Amplifier Class

Class AB

Class AB amplifiers combine Class A and Class B to achieve an amplifier with more efficiency than Class A but with lower distortion than class B.

This is achieved by biasing both transistors so they conduct when the signal is close to zero (the point where class B amplifiers introduce non-linearities). The transistors transition to class B operation for large excursions.

So, for small signals both transistors are active, acting like a class A amplifier. For large signal excursions, only one transistor is active for each half of the waveform, acting like a class B amplifier.

See Also: Amplifier Class

Class B

Class B amplifiers are those in which the output transistors only conduct during half (180 degrees) of the signal waveform. To amplify the entire signal two transistors are used, one conducting for positive output signals and the other conducting for negative outputs.

Class B amplifiers are much more efficient than class A amplifiers, but have high distortion due to the crossover point when the two transistors transition from on to off.

See Also: Amplifier Class

Class C A class C amplifier is a form of switching amplifier in which the transistors are on for less than a half cycle (less than 180 degrees) -- often, much less. For instance, the transistor may be on only during the top 10% of the signal excursion, delivering just a pulse.

Class C amps are very efficient because the transistors are off most of the time and when they are on, they are in full conduction. They deliver high distortion and are often used in RF circuits, where tuning circuits restore some of the original signal and reduce distortion. They are also used in low-fidelity applications where the distortion is not important, such as a siren speaker driver.

Class D

Class D amplifiers are those that output a switching waveform, at a frequency far higher than the highest audio signal that needs to be reproduced. The low-pass filtered, average value of this waveform corresponds to the actual required audio waveform.

Class D amplifiers are highly efficient (often up to 90% or higher) since the output transistors are either fully turned on or off during operation. This completely eliminates the use of the linear region of the transistor which is responsible for the inefficiency of other amplifier types. Modern Class D amplifiers achieve fidelity comparable to class AB.

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Class G Class G amplifiers are similar to class AB amplifiers except they use two or more supply voltages. When operating at low signal levels, the amplifier uses a lower supply voltage. As the signal level increases, the amplifier automatically picks the appropriate supply voltage.

Class G amplifiers are more efficient than class AB amplifiers since they use the maximum supply voltage only when required, while a class AB amplifier always uses the maximum supply voltage.

Class H Class H amplifiers modulate the supply voltage to the amplifier output devices so that it is never higher than necessary to support the signal swing. This reduces dissipation across the output devices connected to that supply and allows the amplifier to operate with an optimized class AB efficiency regardless of output power level.

Class H amplifiers are generally more complex than other designs, with extra control circuitry required to predict and control the supply voltage.


Click-and-pop refers to the unwanted transient signals in the audio band that are reproduced by the headphone and/or speaker when the audio device driving it is either:

  • powered up (power applied)
  • powered down (power removed)
  • brought out of shutdown (power applied previously)
  • forced into shutdown (power still applied)

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Click/Pop Reduction A feature that eliminates "clicks" and "pops" — unwanted transient noise signals during power-up, shutdown, connection, etc.
Clock and Data Recovery The process of extracting and reconstructing clock and data information from a single-wire/channel, serial data stream.
Clock Jitter

A periodic waveform (especially a clock) is expected to cross certain thresholds at precisely timed moments. Variations from this ideal are called jitter.

Learn More:

Clock Throttling Reducing the frequency or duty-cycling the clock of an integrated circuit usually for the purpose of reducing heat generation.
Clock Timing

Electronic devices perform tasks in response to the periodic oscillation of an electrically varying digital voltage that acts as a clock timing signal. On the other hand, human time (also known as “real” time) is measured in seconds, minutes, hours, days, months, and years as dictated by the rotational cycles of the earth. For electronic devices, such as a smart watch, to perform their tasks when required by a user, they must store a digital representation of real time, which is then kept in sync by the digital clock timing signal. In an electronic device, clock timing information is maintained by its Real Time Clock (RTC) circuitry. This will usually be located within the device microcontroller or may be a separate IC on the system board

real time clock timing

Figure 1 Clock timing can be provided by a discrete RTC IC on a system board

Why Use an RTC?

If the main power source for an electronic device fails, then real-time clock timing information will be lost and will need to be reset once power has been restored. While many portable IoT devices have the functionality to reset the time using a wireless connection to a remote master, 2 this type of communication places an extra power drain on the battery (and obviously can only occur if a wireless signal is available). In the absence of a wireless signal, the only (and clearly less desirable) alternative is for the user to manually reset the time, which may not be always straightforward or even possible. An RTC circuit allows a system to keep track of real time long after a main power failure.

Where Are RTCs Used?

Clock timing is important in many different applications, such as industrial (utility meters, point-of-sale equipment, fire alarms, gaming machines, video security), consumer (digital cameras, portable GPS devices, mobile game devices, satellite receivers, TVs) as well as in portable and home medical equipment.

How Does an RTC Keep Time?

A 32.768kHz quartz tuning-fork crystal oscillator is the standard clock timing reference for most electronic applications. The real-time clock maintains timing and date information by counting seconds, which requires a 1Hz clock signal derived from the 32.768kHz crystal oscillator. The time and date information are stored in a set of registers, which is accessed through a communication interface, such as I2C. The crystal may be external to the RTC or integrated within the same package. For applications requiring higher accuracy, an integrated MEMS (microelectromechanical system) resonator is used as the clock timing reference.

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cm Centimeter: 1/100 of a meter, 0.39 inches.
CMF Current-mode feedback
CMI Code matrix insertion
CML Current-mode logic
CMOS Complementary metal-oxide semiconductor technology in which p- and n-channel MOS transistors are used in tandem.

Common Mode Rejection Ratio: The ability of a differential amplifier to not pass (reject) the portion of the signal common to both the + and - inputs.

Learn More: Understanding Common-Mode Signals

CNC Computer numeric control
CO Coarse offset
CODEC Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both.
COG Chip-on-glass
Coherent Sampling

Coherent sampling describes the sampling of a periodic signal, where an integer number of its cycles fits into a predefined sampling window.

Learn More:

COLC Correction loop capacitor
Color Subcarrier

A color subcarrier is a modulated carrier, added to a television signal, to carry the color components.

Examples: In NTSC television, a 3.579545MHz color subcarrier is quadrature-modulated by two color-difference signals and added to the luminance signal. The PAL television standard uses a subcarrier frequency of 4.43362MHz.

Learn More: Video Basics

Common-Mode Signals

Common-mode signals are identical signal components on both the + and - inputs of a differential amplifier or instrumentation amplifier. A common example is in a balanced pair, where a noise voltage is induced in both conductors. Another example is where a DC component is added (e.g. due to a difference in ground between the signal source and the receiver).

In an ideal differential amp, the common-mode element is cancelled out, since the differential (+ and -) inputs should subtract out the identical components. A measurement of the actual ability to do this is called the Common Mode Rejection Ratio, or CMRR.

Learn More: Understanding Common-Mode Signals

Comp. Prop. Delay Comparator propagation delay. This is the lag between the input crossing the comparator threshold, and the output changing states.

Signal processing technique which uses both compression and expansion to improve dynamic range and signal-to-noise ratio.

A signal is passed through a non-linear transformation prior to transmission. A reverse of this transformation occurs at reception. The transformation is such that quiet portions are boosted and loud portions reduced. Noise is reduced because the quiet signals are louder, compared to the noise in the transmission channel.

Used in digital, PCM, transmissions as well as analog applications. Dolby is a common example of a compander-based noise reduction system.


A comparator compares two input voltages and outputs a binary signal indicating which is larger. If the non-inverting (+) input is greater than the inverting (-) input, the output goes high. If the inverting input is greater than the non-inverting, the output goes low.

What is a comparator used for?

The most frequent application for comparators is the comparison between a voltage and a stable reference. Comparators have many applications, including threshold detectors/discriminators, zero-crossing detectors, and oscillators.

What are the types of comparator?

The two basic types of voltage comparator are inverting and non-inverting, depending on which terminal the input signal is applied to.

In an inverting comparator (or negative voltage comparator), the input signal is applied to the inverting terminal and the reference voltage is at the non-inverting terminal. This creates a positive voltage output if the input voltage is less than the reference voltage.

In a non-inverting comparator, the input signal is applied to the non-inverting terminal and the reference voltage is at the inverting terminal. This creates a positive voltage output if the input voltage is greater than the reference voltage.

How do you make a comparator?

A simple comparator can be achieved using an op amp without negative feedback. Its high voltage gain enables it to resolve very small differences in input voltage. Comparators can improve upon this basic design with added features, such as hysteresis and internal references.

See our comparator page and app notes below for more details on how comparators work, their specifications, common comparator features, and how to select a comparator that best fits your needs.

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Complete Central Office Line Interface Central Office Line: telephone line
CompoNet CompoNet is a four-wire, industrial, bus with a master-slave architecture. It is used at the lower network levels to transmit bit or word information, such as for use in sensors and actuators. Up to 256 slaves are supported on a bus. Data rates of 93.75kbps to 4Mbps and network lengths up to 1500 meters with repeaters are possible. CIP is used as the underlying protocol.
Contact Bounce

When a mechanical switch or relay closes, the switch elements will often bounce, even if only briefly, before making final contact. This is of consequence if downstream elements are sensitive to the switching transients. A contact debouncing circuit is often used to remove the transients.

Learn More: Circuit Removes Relay-Contact Bounce

Contact Discharge An ESD test method where the ESD generator makes direct contact with the device under test (DUT).
Coplanar Line

A coplanar line is a line which is in the same plane as another line. Any two intersecting lines must lie in the same plane, and therefore be coplanar.


Coulomb (abbreviated C) is the standard measure of electrical charge.

Named after Charles-Augustin de Coulomb, it is the amount of charge accumulated on a one-farad capacitor charged to one volt; or the amount of charge transported by a one ampere current in one second.

CP Comparable part
CPGA Ceramic pin grid array, an IC packaging technology.
CRC Cyclic Redundancy Check: A check value calculated from the data, to catch most transmission errors. A decoder calculates the CRC for the received data and compares it to the CRC that the encoder calculated, which is appended to the data. A mismatch indicates that the data was corrupted in transit. Depending on the algorithm and number of CRC bits, come CRCs contain enough redundant information that they can be used to correct the data.
CRIL Command register and interface logic
Crossover In an output stage (or similar amplifying stage which uses one device to pull the signal up and another to pull the signal down), the region in which the high-side device is turning on and the low-side device is turning off, or vice versa.
Crowbar Circuit

A crowbar circuit is a power supply protection circuit that rapidly short-circuits ("crowbars") the supply line if the voltage and/or current exceeds defined limits.

In practice, the resulting short blows a fuse or triggers other protection, effectively shutting down the supply.

It is usually achieved by an SCR or other silicon device, or by a mechanical shorting device.

Probably named for the concept of using a big metal bar to mechanically provide the short circuit, as might be used done in a high-current application; or from the appearance of a crowbar circuit's I-V curve.

Learn More:

See Also: Overvoltage Protection


A cathode ray tube (CRT) is a display device which uses an electron beam to energize a phosphorescent coating.

The beam is generated at one end of an evacuated glass tube and controlled by electrostatic and/or electromagnetic fields to strike the coating at the other end, where light emitted when electrons strike the phosphor constitute the display.

Learn More: Electronic Displays Comparison


The art and science of breaking encryption or any form of cryptography.


Cryptography is the practice of securing communication so that the content being sent is only visible to the sender and the intended recipient.

A modern cryptographic system has four main goals:

  • Confidentiality: Information can never be disclosed to someone who is not authorized to see it.
  • Identification and Authentication: Before any information is exchanged, identify and then authorize both the sender and the recipient.
  • Integrity: Information must not be modified in storage or transit. Any modification must be detectable.
  • Non-repudiation: Cannot disclaim the creation/transmission of the message. This provides “digital” legitimacy and traceability of a transaction.

Current cryptographic systems provide all the above or a combination of the above in various forms for an intended application. For more on each of these goals and how they are achieved, see Cryptography: How It Helps in Our Digital World.

What is cryptography used for?

Cryptography is used everywhere in our daily lives. Each time you make an online purchase, conduct a banking transaction, or ping your email client, cryptography is working in the background. It secures all transmitted information in our IoT world to authenticate people and devices, and devices to other devices.

What are the types of cryptography?

Symmetric keys and asymmetric keys are two basic types of algorithms that are used in modern cryptography. Symmetric algorithms use only private keys (commonly referred to as secret keys) while asymmetric key algorithms use a combination of private and public keys.

Symmetric key algorithms help achieve confidentiality using private (secret) keys.

Symmetric key algorithms help achieve confidentiality using private (secret) keys.

Symmetric cryptography (secret key)- In symmetric key cryptography, the sender and receiver share a secret key. That key has to be securely agreed upon before the actual message is sent. To send a message, the sender processes plaintext data using an encryption algorithm under the control of the secret shared key. The result is ciphertext, a scrambled set of data that's useless without knowledge of the key. The encryption algorithm itself is not secret and, in most cases, is publicly known. Once the ciphertext is created, it can be transmitted on a public channel. The recipient then applies the ciphertext and the secret shared key to the decryption algorithm, and the original plaintext is recovered. The encryption algorithms are designed so that even similar messages or similar keys will produce wildly divergent ciphertexts. For more on this process, see this short Symmetric Cryptography Video.

Asymmetric key algorithm helps achieve confidentiality through the use of public and private keys.

Asymmetric key algorithm helps achieve confidentiality through the use of public and private keys.

Asymmetric cryptography (public key)- In asymmetric cryptography, one party (usually the recipient) employs a mathematical algorithm to create a pair of different but cryptographically related keys. The recipient sends one of the keys, designated the public key, to the sender, using an insecure public channel (such as the internet). The sender gets the public key, and uses it along with a publicly known algorithm to encrypt the plain text message. The result is ciphertext. Unlike symmetric encryption, in which the secret shared key has to be kept secret, the public key in an asymmetric cipher is published to everyone, and the public encryption key provides no clue about how to decrypt the message. When the recipient gets the ciphertext message, they recover the plain text message using a decryption algorithm and the private decryption key. For more on this process, see this short Asymmetric Cryptography Video.

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CS Chip select

Chip Scale Package (UCSP or CSP) is an IC packaging technology in which solder balls take the place of pins, making the smallest package available. When heated, the solder balls alloy to matching pads on the circuit board.

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CTIM Retry timeout capacitor
CTON Startup timer capacitor
Current Mode Feedback An alternative op amp topology usually used in high-speed amplifiers. It is sensitive to feedback impedance, and cannot be used as an integrator.
Current-Mode Controller A DC-DC switching regulator which regulates its output voltage by varying the peak inductor current on a cycle-by-cycle basis to output a regulated voltage despite variations in load-current and input-voltage.
Current-Sense Amplifier

A current-sense amplifier is an amplifier that measures current by measuring the voltage drop across a resistor placed in the current path. The current sense amp outputs either a voltage or a current that is proportional to the current through the measured path.

Learn More: Current-Sense Amplifiers

D Flip-Flop

A D (or Delay) Flip Flop (Figure 1) is a digital electronic circuit used to delay the change of state of its output signal (Q) until the next rising edge of a clock timing input signal occurs.

Delay Flip Flop

The truth table for the D Flip Flop is shown in Figure 2.

Delay Flip Flop

What is the D Flip Flop used for?

The D Flip Flop acts as an electronic memory component since the output remains constant unless deliberately changed by altering the state of the D input followed by a rising clock signal.

Where are D Flip Flops used?

The D Flip Flop is a building block shift registers. For example, by cascading eight D Flip Flops in sequence, a byte (8-bits) of information can be stored after 8 clock cycles.

What else can they be used for?

By connecting the inverting output of the D Flip Flop to the D input, a simple divide by two circuit is created i.e. the D output changes state at half the frequency of the clock signal. By cascading D flip flops and through appropriate design of external combinational logic gates, a countdown timer can be created.

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D/A Converter

A Digital-to-analog converter (DAC) is a data converter that receives digital data (a stream of numbers) and outputs a voltage or current proportional to the value of the digital data.

Learn More: Digital-to-Analog Converters

Daisy Chain

Daisy-chaining is a method of propagating signals along a bus in which the devices are connected in series and the signal passed from one device to the next. The daisy chain scheme permits assignment of device priorities based on the electrical position of the device on the bus.

Learn More: How to Daisy-Chain SPI Devices

Dallastat Trademark for Dallas Semiconductor's line of digital rheostats (digital potentiometers). (Dallas Semiconductor is a subsidiary of Maxim Integrated.)
Data Acquisition System System which acquires data, generally by digitizing analog channels and storing the data in digital form. These systems can be standalone or married to a computer and can acquire multiple channels of data.
Data Converter

In electronics, a data converter is a circuit that converts analog to digital or vice-versa. An A/D converter (or ADC) converts a continuously varying analog signal to a stream of digital numbers representing the signal at various points in time. A D/A converter (DAC) does the reverse.


Analog-to-Digital Converters (or A/D converters or ADCs) are circuits that convert analog signals into a stream of digital data.

Types of ADCs

The most common ADC architectures are successive-approximation-register (SAR), sigma-delta, integrating, flash (or direct conversion), pipelined, and two-step. For an introduction to these six types of ADCs, see Tutorial 2094: A Simple ADC Comparison Matrix.

What is the best ADC for my application?

Choosing the right ADC requires tradeoffs between resolution, channel count, power consumption, size, conversion time, static performance, dynamic performance, and price. For low-speed applications, a sigma-delta ADC is likely the best. Faster signals likely require a SAR ADC or pipeline ADC. For more information, see Tutorial 6139: Selecting the Right ADC for Your Application.


Digital-to-Analog Converters (or D/A converters or DACs) receive digital data (a stream of numbers) and output a voltage or current proportional to the value of the digital data.

What is the best DAC for my application?

When choosing a DAC, it is important to look at parameters such as linearity, resolution, speed, and accuracy. Other choices to keep in mind include serial vs. parallel interface, resolution/number of bits, number of input channels, and voltage or current output. For more information on choosing a DAC, see Tutorial 1055: Digital to Analog Converters are a “Bit” Analog and Tutorial 4025: DACs vs. Digital Potentiometers: Which is Right for My Application?

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dB Decibels: A method for specifying the ratio of two signals.

dB = 10 times the log of the ratio of the power of the two signals. This is equal to 20 times the ratio of their voltages, if the signals are driving equal impedances.

Decibels are also used to describe a signal level by comparing it to a reference level. The reference is usually defined as 0dB and the dB value of the signal is 10 times the log of the signal's power over that of the reference. A letter is sometimes added to signify the reference. For instance, dBm is relative to 0 dBm = 1mW.

dBm A unit that defines a signal level by comparing it to a reference level. The reference level of 0dBm is defined as 1mW. The signal level in dBm is 10 times the log of the signal's power over that of the 0dBm reference.
DBS Direct Broadcast Satellite: A system which broadcasts directly from satellite to the subscriber (end user). Prominent examples in the US are DirecTV and Dish network.
DC Direct current
DC-DC Any of the family of switch-mode voltage regulators, these devices use an inductor to store and transfer energy to the output in discrete packets, resulting in highly efficient power conversion.

See application note 2031, "DC-DC Converter Tutorial" and application note 660, "Regulator topologies for battery-powered systems."
DC-DC Controller A DC-DC converter (switch-mode power supply) in which the power switch (usually a power MOSFET) is external to the IC.
DCE Data communications equipment; interchangeable with DTE
DCM Discontinuous-conduction mode
DCR Direct conversion receiver
DCS Digital Cellular System: Any cellular phone system that uses digital (e.g. TDMA, GSM, CDMA).
DDI Digital data input
DDJ Data-dependent jitter
DDR Memory Double Data Rate Synchronous DRAM: A clock is used to read data from a DRAM. DDR memory reads data on both the rising and falling edge of the clock, achieving a faster data rate. Often used in notebook computers because it also consumes less power.
DDRD Data direction register D

Direct digital synthesis (DDS) is a method for digitally generating analog waveforms, such as sine waves (modulated or not) or arbitrary waveforms.

In the most straightforward realization, a digitized sample of the waveform is stored and the values are clocked out to a D/A converter. Varying the clock rate changes the frequency. Variations in rate and changes to a gain factor can modulate the signal.

Learn More: All About Direct Digital Synthesis


Electrical contacts in mechanical pushbutton switches often make and break contact several times when the button is first pushed. A debouncing circuit removes the resulting ripple signal, and provides a clean transition at its output.

Learn More:

See Also: ESD

DECT Digital European cordless telephone

DeepCover® is a registered trademark for three families of embedded security products that offer advanced physical security to provide the most secure key storage possible. It includes secure authenticators, security managers, and secure microcontrollers.

DeepCover Secure Microcontrollers integrate advanced physical security to offer the highest level of protection against physical tampering and reverse engineering.

DeepCover Security Managers combine advanced physical security with on-chip, nonimprinting memory to safeguard sensitive data from the slightest physical or environmental tampering.

DeepCover Secure Authenticators implement advanced physical security to provide the ultimate in low-cost IP protection, clone prevention, and peripheral authentication.

DeepCover is a registered trademark of Maxim Integrated Products, Inc.

Learn More: DeepCover Embedded Security Technology


An analog-to-digital converter (ADC) architecture consisting of a 1-bit ADC and filtering circuitry which over-samples the input signal and performs noise-shaping to achieve a high-resolution digital output. The architecture is relatively inexpensive compared to other ADC architectures.

Sometimes called a "sigma-delta" converter.

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Design for Testability Design For Testability (or Design for Test, or DFT) refers to design techniques that make products easier to test. Examples include the addition of test points, parametric measurement devices, self-test diagnotics, test modes, and scan design.
Deterministic Jitter

Deterministic jitter (or bounded jitter) is reproducible jitter within a given system, under controlled conditions.

Learn More:

See Also:

DFE Decision feedback equalization
DFMEA Design Failure Mode and Effects Analysis (DFMEA) is a method for evaluating a design for robustness against potential failures.
DG Differential gain
Difference Amplifier

A difference amplifier is a circuit that takes two inputs and outputs the difference between them. It is a special case of the differential amplifier with a gain of 1. It is also referred to as a voltage subtractor.

What does a difference amplifier do?

A difference amplifier outputs the difference between its inputs.


In an ideal difference or differential amp, the output depends only on the difference between the two inputs. In any real differential amp, the output also depends on the average of the two inputs, which is called the common mode of the amp.


The common mode rejection ratio (CMRR) is a measure of a device’s ability to reject this signal. Differential amps are very common in analog circuit design and are particularly useful in electronically noisy environments because of their ability to cancel out unwanted noise.

What is the difference between a difference amplifier and a differential amplifier?

The term “difference amplifier” can be used to refer to a type of differential amplifier with a gain of 1. For this reason, it can also be referred to as a unity gain differential amplifier. A differential amp has an output proportional to the difference between inputs, and a difference amp has an output equal to the difference between inputs. The two terms are also often used interchangeably.

What is the difference between a difference amplifier and an instrumentation amplifier?

Difference amplifiers and instrumentation amplifiers are both types of differential amplifier circuits. An instrumentation amplifier is a type of differential amplifier with input buffer amplifiers that eliminate the need for impedance matching. The gain can be adjusted through the variation of just one resistor. Instrumentation amplifiers are also available as ICs that provide very high CMRR.

Learn More: Amplifiers

Differential Amplifier

What is a differential amplifier?

A differential (or difference) amplifier is a two-input circuit that amplifies only the difference between its two inputs. An operational amplifier or op-amp (Figure 1) is an example of a difference amplifier. The formula that describes the behavior of the circuit is:

Vout = A * (Vin+ - Vin-) where A is the gain of the amplifier

Operational Amplifier Symbol

Figure 1. Operational Amplifier Symbol

What are differential amplifiers used for?

Differential amplifiers are useful in electrically noisy environments where a low amplitude electrical signal can be easily corrupted by the effect of unwanted external noise. In this scenario, a single-ended amplifier would be unsuitable since it would also amplify the unwanted noise signal as well as the desired input signal. A differential amplifier works on the principle that unwanted electrical noise couples equally onto both input terminals of the amplifier and will therefore be rejected allowing only the wanted signal to be amplified.

Where are differential amplifiers used?

They are used at the front end of analog systems being used to detect a low amplitude electrical signal e.g. an ECG monitor to detect heart rate where the electrical signal may be of the order of only a few millivolts. The purpose of the differential amplifier is to increase the amplitude of the heart signal to a level where it can be converted into a digital form. The gain of the circuit can be adjusted by appropriate selection of external resistors connected between the output and input terminals.

Learn More:

Differential Remote Output Sensing Uses a Kelvin connection at a remote location to sense the output voltage and better control the voltage at that point.
Differential Signaling

Most electrical signals are single-ended, comprised of a single wire and ground. Differential signals use two wires which are the inverse of each other -- when one swings positive, the other swings negative in equal magnitude.

The receiving circuit looks only at the difference between the two, ignoring any common-mode voltage. This "push-pull" arrangement reduces the impact of electrical interference because external noise will affect both wires equally and the common-mode rejection will ignore the noise.

Examples: RS-422, RS-485, professional audio signal standards (especially for microphones), the signal lines employed by Ethernet, and the standard twisted-pair analog telephone (POTS) line.

Learn More: Understanding Common-Mode Signals

Digital Log Pot Digital logarithmic potentiometer.
Digital Pot

A digital potentiometer (or digital pot) is a solid-state device that emulates a mechanical potentiometer, usually controlled via a simple interface.

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Digital Signal Processor A Digital Signal Processor, or DSP, is a special-purpose digital circuit that acts on digitized signals, such as audio. DSP circuits can replace traditional analog functions, such as filtering and more complex functions that are difficult to accomplish in the analog domain.

A Digital Audio Signal Processor is a DSP for audio applications.

DIO Data input/output
Diode A two-terminal device that rectifies signals (passes current in only one direction). Most commonly, a semiconductor consisting of a P-N junction, but diodes can also be realized using vacuum tube, point-contact, metal-semiconductor junction (Schottky), and other technologies.

DIP (Dual Inline Package) is an integrated circuit package with two rows of pins.

PDIP (Plastic Dual Inline Package) is a DIP package with a molded plastic body.

CDIP (Ceramic Dual Inline Package) is a DIP package with a ceramic body.

Learn More: Package Materials


In systems that handle electrical signals, distortion is a generally unwanted change in the signal.

Not all signal alterations are considered distortion. For instance, a uniform delay or a linear attenuation or amplification would generally not be considered distortion.

See Also:


Dithering is a common technique to improve digitizing when quantization noise (quantization error/noise) can no longer be treated as random.

A small amount of random noise is added to the analog input signal. This added noise causes the digital output to randomly toggle between two adjacent codes, thereby avoiding thresholding effect.

DIU Digital interface unit
Diversity In radio systems, diversity is a method of improving the reliability and capacity by using multiple communication channels to carry each signal.
DLC Double-layer capacitor
DMA Direct Memory Access: A scheme which reads or writes data directly to memory, bypassing the processor and the processor bus.
DML Data Manipulation Language (or Data Management Language): A language that allows data to be manipulated in a database. In SQL, commands such as DELETE and INSERT are DML commands.
DMM Digital Multimeter: Measuring instrument or VOM (e.g. voltage, resistance, current) with a digital display.
DMR Digital microwave radio
DMT Discrete multitone data transmission

Differential Nonlinearity: A specification that appears in data-converter datasheets. In an ideal D/A converter, incrementing the digital code by 1 changes the output voltage by an amount that does not vary across the device's permitted range. Similarly, in an A/D, the digital value ramps smoothly as the input is linearly swept across its entire range. DNL measures the deviation from the ideal. An ideal converter has the code exactly the same size, and a DNL of 0 (zero).

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DOCSIS Data Over Cable Service Interface Specification: A standard for delivering data over cable TV systems, typically for subscriber Internet access services.
Down Converters A device which provides frequency conversion to a lower frequency, e.g. in digital broadcast satellite applications.
DP Differential phase; also decimal place
DPAK Discrete packaging
DPD Digital phase detector
DPDT Double-pole/double-throw
DPH Data pointer high
DPL Data pointer low
DPM Digital panel meter
DPS Data pointer select
DPST Double-pole/single-throw
DPWM Digitally adjusted pulse-width modulation
DQPSK Differential quadrature phase-shift keying

One of the three terminals that comprise a FET. A voltage on the gate controls the current flow between the source and drain.

DRAM Dynamic RAM: Random-Access Memory that uses a continuous clock. Unlike SRAM, when DRAM is no longer clocked, its data is lost.
DRC Design-rule checking
DRL Daytime Running Lamps (DRLs) are white lights mounted on the front of an automobile. Mandated in many countries, they automatically switch on when the key is turned and are intended for daytime use, to increase the visibility of the automobile. They are typically built with LEDs.

See: High-Brightness LED Drivers

Drypack Drypack is a method for packing integrated circuits in a moisture-free environment. The device is baked and immediately sealed in a vacuum-sealed bag.

This process is reserved for package types which are especially susceptible to moisture intrusion. Maxim devices with MSL (Moisture Sensitivity Level) of 2 or higher require drypack. A part-number suffix of -D, +D, or #D at the end of the part number denotes products which ship with drypack. There is no price adder associated with drypacking products with MSL 2 or above.

DSL A mechanism for providing high-speed digital communications (e.g. Internet access) over a standard phone line.
DSLAM Digital Subscriber Line Access Multiplexer: a device which takes a number of ADSL subscriber lines and concentrates these to a single ATM line.
DSSP Digital-sensor signal processor
DSSS Direct-Sequence Spread Spectrum: A transmission technology used in WLAN (wireless LAN) transmissions where a data signal at the sending station is combined with a higher data-rate bit sequence, or chipping code, that divides the user data according to a spreading ratio.

See: "An Introduction to Direct-Sequence Spread-Spectrum Communications".

DTB Digital terrestrial broadcasting
DTE Data terminal equipment; interchangeable with DCE
DTMF Dual Tone Multiple Frequency (DTMF) is a signaling method developed by Bell Labs for sending telephone dialing information over the same analog, voice-quality phones lines that carry voice.

Each digit is encoded as the sum of two sine wave bursts, of different frequencies. The two-tone method was chosen because it can be reliably distinguished from voice and normal phone conversations are highly unlikely to falsely trigger the DTMF receiver.

DTMF was the basis for "TouchTone" (a former trademark of AT&T), the pushbutton system that replaced mechanical rotary dial telephones.

Dual Mode Two modes of operation. Examples: In power circuits, the IC can deliver either a fixed 5V or an adjustable 1.3V to 16V source. In cellular phones, the IC operates in FM or CDMA mode, AMPS or TDMA mode, etc.

(Maxim Integrated trademarked term.)

Dual Phase Controller Switching regulator that employs dual-phase technique to reduce output noise and boost output current capability.
Dual-Band Dual-band refers to the capability of GSM network infrastructure and handsets to operate across two frequency bands.
Dual-Modulus Prescaler

A Dual-Modulus Prescaler (DMP) is an important circuit block used in frequency synthesizers to divide the high-frequency signal from the voltage controlled oscillator (VCO) to a low-frequency signal by a predetermined divide ratio, either (N+1) or N, which is controlled by a swallow counter.

This low-frequency signal is then further divided by the main counter to the desired channel-spacing frequency which is then fed to the phase detector to form the closed feedback loop in frequency synthesizers.

DVB Digital Video Broadcast is a name for digital TV.
DVM Digital voltmeter
DWDM Dense Wave Division Multiplexing: The technology by which the frequencies of light carried on a single optical fiber are subdivided into discrete wavelengths, allowing for the greater transmission of data.
DXC Digital cross-connect
Dynamic Range The range, in dB, between the noise floor of a device and its defined maximum output level.
E1 Wide-area, digital transmission scheme, used predominantly in Europe, that carries data at a rate of 2.048Mbps. E1 lines can be leased for private use from common carriers.
E2 A line that carries four multiplexed E1 signals with a data rate of 8.448Mbps.
E3 Wide-area, digital transmission scheme used predominantly in Europe that carries data at a rate of 34.368Mbps. E3 lines can be leased for private use from common carriers.
EAM Electro-Absorption Modulators: Chip-level modulation devices often integrated into hybrid transponder devices, alongside lasers.
ECB Electrically controlled birefringence
ECL Emitter-coupled logic
ECM Electret capacitor microphone
EconoReset The simplest form of microprocessor supervisory circuit, it monitors the power supply for the microprocessor and provides only a power-on reset function.
EconOscillator Low-cost, surface-mount, CMOS oscillator family from Maxim. EconOscillators replace crystal-based oscillators. They need no external crystals or timing components.

See: EconOscillator product index for additional descriptions, features, etc.

EconOscillator is a trademark of Maxim Integrated
EDFA Erbium-doped fiber-optical amplifier
EDGE Enhanced Data Rates for GSM Evolution: An enhanced modulation technique designed to increase network capacity and data rates in GSM networks. EDGE should provide data rates up to 384Kbps.
EEPROM Electrically erasable programmable read-only memory
EFT Electrical fast transient
EIA Electronic Industries Alliance: Among other things, the EIA sponsors electrical and electronic standards.
EIA-JEDEC Electronic Industries Association/Joint Electron Device Engineering Council
Embedded System

A system in which the computer (generally a microcontroller or microprocessor) is included as an integral part of the system.

Often, the computer is relatively invisible to the user, without obvious applications, files, or operating systems. Examples of products with invisible embedded systems are the controller that runs a microwave oven or the engine control system of a modern automobile.

EMC Electromagnetic Compatibility: The ability of electronic equipment to be a "good electromagnetic neighbor": It neither causes, nor is susceptible to, electromagnetic interference (within the limits of applicable standards).
EMI Electromagnetic Interference: Unwanted noise from electromagnetic radiation.

See: EMI Reduction Solutions page.

End Point Behavior of the device at the limit of temperature or voltage.
ENDEC Encoder/Decoder
Energy Harvesting

Energy harvesting (also known as power harvesting or energy scavenging) is the process in which energy is captured from a system's environment and converted into usable electric power. Energy harvesting allows electronics to operate where there's no conventional power source, eliminating the need to run wires or make frequent visits to replace batteries.

An energy harvesting system generally includes circuitry to charge an energy storage cell, and manage the power, providing regulation and protection.

What are the types of energy harvesting?

Types of energy harvesting

Energy source examples include light (captured by photovoltaic cells), vibration or pressure (captured by a piezoelectric element), temperature differentials (captured by a thermo-electric generator) radio energy (captured by an antenna); and even biochemically produced energy (such as cells that extract energy from blood sugar).

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Effective Number of Bits (ENOB) is an indication of the quality of an analog-to-digital converter (ADC). The measurement is related to the test frequency and the signal-to-noise ratio.

Learn More:

EPON Ethernet (-based) passive optical network
EPROM Erasable programmable read-only memory
ERC Extinction ratio control
ESBGA Enhanced Super Ball-Grid Array (trademark of Amkor/Anam)

Electrostatic Discharge (ESD) is the release of stored static electricity. Most commonly, the potentially damaging discharge of many thousands of volts that occurs when an electronic device is touched by a charged body.

See the below application notes and video that describe how ESD is generated, how it damages electronic systems, human body and machine models for testing, IEC compliance levels, and design approaches.

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ESD Protection Devices added to input and output pins on an IC to protect the internal circuitry from the damaging effect of electrostatic discharge.

See: ESD Overview.

ESF Extended Superframe: A DS1 framing format in which 24 DS0 times lots, plus a coded framing bit are organized into a frame which is repeated 24 times to form a superframe.
ESL Effective/Equivalent Series Inductance is the parasitic inductance in a capacitor or resistor.
ESP Extended stack pointer
ESR Effective Series Resistance (or Equivalent Series Resistance or ESR) is the resistive component of a capacitor's equivalent circuit.

A capacitor can be modeled as an ideal capacitor in series with a resistor and an inductor. The resistor's value is the ESR.

Ethernet A family of network protocols based on asynchronous frames. The Ethernet framing structure provides a flexible payload container with basic addressing and error detection mechanisms.
EV 1. Electric Vehicle.

2. Evaluation, as in "EV Kit."

Evaluation Kit Evaluation Kit (EV Kit, Development Kit): A printed circuit board with an integrated circuit and support components to produce a working circuit for evaluation and development. Most Evaluation Kits are fully assembled and tested.

EVKIT: Part number suffix used for Maxim Evaluation Kits.

Dallas Semiconductor, now owned by Maxim, used the term "development kit."

EVM Error Vector Magnitude: A measure of the difference between the (ideal) waveform and the measured waveform. The difference is called the error vector, usually referred to with regard to M-ary I/Q modulation schemes like QPSK, and shown on an I/Q "constellation" plot of the demodulated symbols. Also see: "Phase Noise and TD-SCDMA UE Receiver,"
EVSE EVSE is an abbreviation for Electric Vehicle Service Equipment, referring to a charging station.

See: Application Note 5348: G3-PLC Technology Finally Makes Charging an Electric Vehicle Smart

EVSYS Evaluation System: Evaluation kits that also include an interface board for connecting to a personal computer and Windows-based EVKit software.

EVSYS: Suffix used for Maxim Evaluation System part numbers.

Exposed Pad Offered in some packages to improve thermal dissipation or lower the impedance of the ground connection. Normally not electrically isolated, it typically needs to be connected to a ground or power plane, depending on the device.
F 1. Farad(s): Unit of capacitance.

2. f in lower case is the standard abbreviation for femto, a metric prefix for 10 to the -15.

3. Fahrenheit temperature scale.

fA Femtoampere(s): 10 to the -15 Ampere; a millionth a nanoampere.
Fail-Safe A technique used in RS-485 interface transceivers which forces the output to a predefined state in the event of a line short or open circuit.
Fan Controller - Linear An integrated circuit that varies the speed and airflow of a cooling fan using a variable voltage in response to temperature or system commands.
Fan Controller - PWM An integrated circuit that varies the speed and airflow of a cooling fan using a pulse-width-modulated (PWM) voltage in response to temperature or system commands.
Fault Blanking A function that ignores a fault for a predetermined period. This is done to eliminate nuisance fault indication.
Fault Tolerant Will tolerate excessive voltage during a fault condition.
FB Feedback
FCD Fan count divisor
FCR Fan conversion rate
FDD Frequency-division duplex
FDDI Fiber Distributed Data Interface: A standard for transmitting data on optical fiber cables at a rate of around 100,000,000 bits-per-second (10 times as fast as 10 Base-T Ethernet; about twice as fast as T-3).
FDL Facility data link: Embedded communications channel in ESF DS1 framing. Used to convey both bit-oriented and message-oriented signals.
FDM A method for carrying multiple channels of information on one channel by dividing the available bandwidth among the channels.
FE Functional equivalent (in component cross-reference data); also field engineer; also framing error
FEC Forward Error Correction: A technique for detecting and correcting errors from imperfect transmission by adding a small number of extra bits. FEC allows optical transmission over longer distances by correcting errors that can happen as the signal-to-noise ratio decreases with distance.
Femto Base Station A femto base station (also called an Access Point Base Station, femtocell, femtobasestation or femto basestation) is an in-home base station. Like a standard base station, it connects cell phone voice and data to the cell phone network, but it serves a smaller area (the home).

A femto base station benefits the service provider because it offloads cell tower traffic. Subscribers benefit from superior signal strength, due to the proximity of the unit -- especially where a cellular signal is weak or not available.

Femto base stations augment the normal network and replicates the usual telecommunications infrastructure. Connection to the cell phone network is provided by VoIP over the Internet.


Field-Effect Transistor: A transistor in which the voltage on one terminal (the gate) creates a field that allows or disallows conduction between the other two terminals (the source and drain).

There are three varieties: The JFET (Junction Field-Effect Transistor); the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor); and the MESFET (Metal-Semiconductor Field-Effect Transistor).

The FET is one of two major kinds of transistor, the other being the Bipolar Junction Transistor.

FFT A Fourier transform (FT) converts a signal from the time domain (signal strength as a function of time) to the frequency domain (signal strength as a function of frequency). It shows the signal's spectral content, divided into discrete bins (frequency bands).

The Fast Fourier Transform is a common algorithm for Fourier transforms. It is more efficient (faster) than the DFT, Discrete Fourier Transform.

FG Fan gain
FHSS Frequency Hopping Spread Spectrum: A transmission technology in which the data signal is modulated by a narrowband carrier signal which changes frequency ("hops") over a wide band of frequencies. The hopping seems random but is prescribed by an algorithm known to the receiving system.
Fibre Channel A highly-reliable, gigabit interconnect technology that allows concurrent communications among workstations, mainframes, servers, data storage systems, and other peripherals using SCSI and IP protocols. It provides interconnect systems for multiple topologies that can scale to a total system bandwidth on the order of a terabit per second. (The standardized spelling is "fibre channel" but often misspelled as "fiber channel.")
FIFO First-In First Out: A type of memory that stores data serially, where the first bit read is the first bit that was stored.
FireWire Apple Computer trademarked name for the IEEE 1394 serial interface standard: A high-speed interface between computers and peripherals such as external disk drives, cameras, and camcorders. Also referred to by Sony trademarked name, "I-Link."
FIT Failures in time: See FIT calculator: /en/design/design-tools/calculators/general-engineering/qafits.html
Flash ADCs

An analog-to-digital converter that uses a series of comparators with different threshold voltages to convert an analog signal to a digital output.

Learn More: Understanding Flash ADCs

FlexSound FlexSound describes a set of digital audio signal processing blocks used in Maxim's products to provide or enhance audio functions such as compression, limiting, or equalization.

FlexSound® processor is a fully programmable digital audio signal processing system that includes a programmable DSP core, hard-wired digital macros, and an associated memory architecture.

FlexSound is a registered trademark of Maxim Integrated Products, Inc.
  1. A signal line is said to be "floating" if it is not connected to any voltage supply, ground, or ground-referenced signal source.


    • An open-drain, high-impedance (hi-z) output when in the off (hi-z) mode
    • In microcomputer systems, a data or address bus may, at times, be undriven (floating). This is permissible because control signals indicate when data is valid, so users of the bus know when the signal can be ignored.

  2. One form of non-volatile memory device is achieved via floating gates. The gate of a MOSFET has no connection, allowing charge to remain indefinitely. The gate charge is changed using Fowler-Nordheim tunneling or hot-carrier injection. EPROM, EEPROM, and flash memory are examples.

    Learn More: Memory Products


Frequency Modulation (FM) is a modulation method in which the carrier frequency changes with the input signal amplitude.

FM Modulation

FM modulation (frequency modulation) refers to the superposition (modulation) of a lower frequency analog data (information) signal onto a higher frequency sinewave carrier signal.

What is the difference between FM Modulation and AM Modulation?

With AM modulation (amplitude modulation), the information signal varies the amplitude of the carrier signal i.e. the size of the carrier signal varies but the frequency remains constant. With FM modulation, the amplitude remains constant, but the frequency varies.

AM and FM Waveforms

Figure 1. AM and FM Waveforms

Why is modulation required?

The higher the frequency of the carrier signal, the shorter the size of the antenna (aerial) required to detect and receive the signal. FM radio stations can be received using an antenna typically less than 1 meter in length, a convenient size for a typical FM receiver.

How is FM Modulation performed?

Generation of an FM signal requires a voltage-controlled oscillator (VCO) circuit. This can be designed and then built using discrete components, but they are also available as integrated circuits (ICs).

How is the analog data signal recovered from the modulated signal?

Once the modulated signal has been detected and received, the analog data signal can be recovered using a Phase-Locked Loop (PLL) circuit.

Can FM only be performed using analog signals?

While the carrier signal is an analog signal, the information signal can be digital. In this scenario, which is referred to as Frequency Shift Keying, only two frequencies are used – one frequency to represent ‘0’ and the other (higher or lower) frequency to represent ‘1’.

Learn MorePhase Locked Loops (PLLs) and Voltage Controlled Oscillators (VCOs)

FOC Fields oriented control
Foldback Current Limit A circuit which reduces the current limit once the device enters current-limited operation. Commonly seen on RS-422/RS-485 drivers and some power circuits.

Measurement technique in which a voltage (or current) is forced at a remote point in a circuit; then the resulting current (or voltage) is measured (sensed).

Learn More: Force/Sense DAC Applications

Forward Converter A power-supply switching circuit that transfers energy to the transformer secondary when the switching transistor is on.
FOX Fast-on oscillator
FPBW Full-power bandwidth
FPGA Field Programmable Gate Array: A family of general-purpose logic devices that can be configured by the end user to perform many, different, complex logic functions. It is often used for prototyping logic hardware.
Frame Relay A high-speed, packet-switched data communications service similar to X.25. Frame relay is a leading contender for LAN-to-LAN interconnect services, and is well suited to the burst-intensive demands of LAN environments.
Framer A device used to align/synchronize to an embedded framing pattern in a serial bit stream. Once synchronized and data fields are properly aligned, overhead bits for alarms, performance monitoring, embedded signaling, etc. may be extracted and processed.
Frequency Bin The frequency range and resolution on the frequency axis of a spectrum graph depends on the sampling rate and the size of the data record (the number of acquisition points). The number of frequency points or lines or bands in the power spectrum is NRECORD/2, where NRECORD is the number of signal points captured in the time domain.

The first frequency line in the power spectrum always represents DC (frequency=0). The last frequency line can be found at fSAMPLE/2 - fSAMPLE/NRECORD. Frequency lines are spaced at even intervals of fSAMPLE/NRECORD. They are commonly referred to as frequency bins or FFT bins. Bins can also be computed with reference to a data converter's sampling period:

Example: We apply a sampling frequency of 82MHz and take 8192 records. The frequency bin is 10kHz.
Frequency Diversity In radio systems, Frequency Diversity spreads a signal across multiple channels by transmitting multiple versions of the signal on different frequencies.
Frequency Synthesizer A frequency synthesizer is an electronic circuit that uses an oscillator to generate a preprogrammed set of stable frequencies with minimal phase noise. Primary applications include wireless/RF devices such as radios, set top boxes, and GPS.
FS Full scale; frame sync
FSC Fan-speed control
FSK Frequency Shift Keying: A method of transmitting digital data by shifting the frequency of a carrier signal to represent binary 1s and 0s.
FSO Full-span output
FSOTC Full-span output temperature coefficient
FSR Full-scale range
FTC Fan tachometer count
FTCL Fan tachometer count limit
FTTB Fiber-to-the-business
FTTH Fiber-to-the-home: A method for broadband data (voice, Internet, multimedia, etc.) delivery to the home via optical fiber.

Contrast with FTTN (fiber-to-the-node) which uses fiber up to a node outside the home and uses copper to bring the data into the home.

FTTN FTTN is "Fiber-to-the-node."

There are two technologies for delivering broadband: Fiber-to-the-node (FTTN) uses fiber to bring data to a node and uses copper to bring the data into the home. Fiber-to-the-home (FTTH) brings fiber all the way into the home.

Full Bridge Rectifier

A rectifier converts an AC signal into DC, and a bridge rectifier does this using a diode bridge. A diode bridge is a system of four or more diodes in a bridge circuit configuration, wherein two circuit branches are branched by a third. A bridge rectifier provides full-wave rectification.

How does a bridge rectifier work?

Since current can only flow in one direction through a diode, current must travel different paths through the diode bridge depending on the polarity of the input. In either case, the polarity of the output remains the same. When there is an AC input, the current travels one path during the positive half cycle, and the other during the negative half cycle. This creates a pulsating DC output since the signal still varies in magnitude, but no longer in direction.

Current flow in a bridge rectifier during the positive half cycle.

Current flow in a bridge rectifier during the positive half cycle.

Current flow in a bridge rectifier during the negative half cycle.

Current flow in a bridge rectifier during the negative half cycle.

What is the difference between a full wave rectifier and a bridge rectifier?

A bridge rectifier is a type of full wave rectifier. A full wave rectifier converts the input waveform to one of constant polarity, as opposed to a half-wave rectifier which only passes one half cycle while blocking the other. Another common method of full wave rectification uses two diodes and a center-tapped transformer. See App Note 6164: Build a Full-Wave Rectifier Circuit with a Single-Supply Op Amp for another method of full-wave rectification.

Why do we use four diodes in a bridge rectifier?

The bridge circuit configuration with four diodes allows for cost-effective full-wave rectification by utilizing two diodes during each half cycle. A half-wave rectifier can be constructed from a single diode, but is less efficient than a full-wave rectifier. A center-tapped rectifier provides full-wave rectification, but with the added cost and size of a center-tapped transformer.

Full Duplex A channel providing simultaneous transmission in both directions.
G Gram(s)
GaAs Gallium arsenide: A semiconductor material used for optoelectronic products such as LEDs, and for high-speed electronic devices.
GaAs MESFET A Gallium Arsenide (GaAs) Metal-Semiconductor Field-Effect-Transistor (MESFET) is a transistor built with gallium arsenide semiconductor material. The conducting channel is built using a metal-semiconductor (Schottky) junction.
GaAsFET Gallium arsenide field-effect transistor
GaAsP Gallium Arsenide Phosphide (or, Gallium Arsenic Phosphide): A semiconductor material used for optoelectronics, including LEDs and photodiodes.
Gain The amount of amplification accomplished by an amplifier circuit. For instance, a gain of 2 would mean the output is scaled to twice the amplitude of the input.
Gain Error

The gain error of a data converter indicates how well the slope of an actual transfer function matches the slope of the ideal transfer function.

Gain error is usually expressed in LSB or as a percent of full-scale range. Gain error can be calibrated out with hardware or in software. Gain error is the full-scale error minus the offset error.

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Galvanic Isolation Galvanic isolation is a design technique that separates electrical circuits to eliminate stray currents. Signals can pass between galvanically isolated circuits, but stray currents, such as differences in ground potential or currents induced by AC power, are blocked.

See: Maxim's isolated RS-485/RS-422 transceivers.

Gamma Correction

Gamma correction is the application of a function that transforms brightness or luminance values. Gamma functions are usually nonlinear but monotonic and designed to affect the highlights (whitest values), midtones (grayscale), and shadows (dark areas) separately.

Most commonly applied to make a light-emitting device, such as a display, match the human eye's brightness curve. In other terms: A gamma correction function can be used to alter the luminance (light intensity) of a display such that its brightness (the human-perceived values) looks correct.

Learn More: Using Lookup Tables to Perform Gamma Correction on LEDs


1. The controlling terminal of a FET. A voltage on the gate controls the current flow between the source and drain.

2. A basic logic element (e.g. AND, OR, NOT, NAND, NOR, XOR, etc.).

GbE Gigabit Ethernet
GBIC Gigabit Interface Converter: A removable transceiver module permitting Fibre-Channel and Gigabit-Ethernet physical-layer transport.
GBW Gain bandwidth

A generator is an electromechanical device that converts mechanical power into electrical power.

See Also: Alternator

GFSK Gaussian frequency-shift keying: A type of FSK modulation which uses a Gaussian filter to shape the pulses before they are modulated. This reduces the spectral bandwidth and out-of-band spectrum, to meet adjacent-channel power rejection requirements.

Bluetooth uses GFSK.


GHz, short for gigahertz, is a unit of frequency equal to one billion hertz. It is commonly used to measure computer processing speed, alternating current, and electromagnetic (EM) frequencies.

When used in terms of computer processing speed, it is the measure of the processor’s clock rate, which is the rate at which it generates pulses to synchronize the operations of its components. This is normally the frequency of a crystal oscillator.

The hertz is defined as one cycle per second (cps) and is named after Heinrich Hertz, who proved the existence of EM waves. It is equivalent to the reciprocal second (s-1).

Hz, kHz, MHz, and GHz

The base unit of frequency is the hertz, which is equal to one cycle per second. Other common units are kHz, MHz, and GHz, which are multiples of Hz following standard SI prefix conventions. A kilohertz is a thousand hertz, a megahertz is a million hertz, and a gigahertz is a billion hertz.






109 Hz (1 billion Hz)



106 Hz (1 million Hz)



103 Hz (1 thousand Hz)



1 Hz

How to convert Hz to kHz to MHz to GHz

These most common units of frequency are multiples of a thousand. For example, since 1 MHz is a million Hz and 1 GHz is a billion Hz, a GHz is a thousand times faster than a MHz. To convert from MHz to GHz, just divide by a thousand. To convert from a larger unit to a smaller one (like from GHz to MHz), then multiply by that value instead.

Gigabit 1 billion bits-per-second.
Glitch General term used to describe an undesirable, momentary pulse or unexpected input or output.
Glitch Immunity A term used in microprocessor supervisory circuit datasheets to describe the maximum magnitude and duration of a negative-going VCC supply-voltage pulse without causing the reset output to assert.
GLONASS The Russian Global Navigation Satellite System
GMSK Gaussian minimum shift keying (GMSK) is a form of frequency shift keying (FSK) used in GSM systems. The tone frequencies are separated by exactly half the bit rate. It has high spectral efficiency.

Gigabit Multimedia Serial Link. This is a Maxim-specific category name for a range of products that serialize, deserialize, and buffer high-speed digital data streams for communications over short distances.

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GPIB General Purpose Interface Bus: A standard bus for controlling electronic instruments with a computer. Also called IEEE-488 bus because it is defined by ANSI/IEEE Standards 488-1978, and 488.2-1987. Also called HP-IB, a trademarked term of Hewlett-Packard, which invented the protocol.
GPIO General Purpose I/O: A flexible parallel interface that allows a variety of custom connections.
GPON Gigabit passive optical network
GPRS General Packet Radio Service: A radio technology for GSM networks that adds packet-switching protocols and shorter set-up time for ISP connections; it offers the possibility to charge by amount of data sent rather than connect time.
GPS Global Positioning System: A satellite- based navigation system in which two or more signals, received from satellites, are used to determine the receiver's position on the globe.
GSM Global System for Mobile Communications: A land, mobile, pan-European, digital, cellular radio-communications system.
GSM900 GSM network operating in the 900MHz band, as used by BT Cellnet and Vodafone in the UK, and by more than one hundred countries around the world.
GUI Graphical user interface
H Henry(ries): The unit of inductance.
H-Bridge A circuit diagram which resembles the letter "H." The load is the horizontal line, connected between two pairs of intersecting lines. It is very common in DC motor-drive applications where switches are used in the "vertical" branches of the "H" to control the direction of current flow, and thus the rotational direction of the motor.
Half-Duplex Data transmission over a circuit capable of transmitting in either direction, but not simultaneously.

An ADC architecture which uses a bank of comparators first to digitize the upper half bits, then uses a digital-to-analog converter (DAC) to subtract that voltage from the input, and then digitizes what remains of the input signal to get the lower half bits.

Learn More: The ABCs of ADCs

Half-Wave Rectifier

A half-wave rectifier converts an AC signal to DC by passing either the negative or positive half-cycle of the waveform and blocking the other. Half-wave rectifiers can be easily constructed using only one diode, but are less efficient than full-wave rectifiers.

Since diodes only carry current in one direction, they can serve as a simple half-wave rectifier. Only passing half of an AC current causes irregularities, so a capacitor is usually used to smooth out the rectified signal before it can be usable.

Half-wave rectifier circuit with capacitor filter and a single diode.

Half-wave rectifier circuit with capacitor filter and a single diode.

Half-wave and full-wave rectifiers

Alternating current (AC) periodically changes direction, and a rectifier converts this signal to a direct current (DC), which only flows in one direction. A half-wave rectifier does this by removing half of the signal. A full-wave rectifier converts the full input waveform to one of constant polarity by reversing the direction of current flow in one half-cycle. One example configuration for full-wave rectification is the full bridge rectifier, which uses four diodes to create a pulsating DC output.

Half-wave and full-wave rectifier waveforms

A half-wave rectifier creates a purely positive signal by blocking the negative half-cycle, while a full-wave rectifier does this by changing the direction of the negative half-cycle.

What is the efficiency of a half-wave rectifier?

Since only half of the input waveform is passed, the efficiency of a half-wave rectifier is lower than that of a full-wave rectifier. The maximum efficiency of a half-wave rectifier is about 40.5%, and the maximum efficiency of a full-wave rectifier is twice that.

Learn More: Half-Wave Rectifier Mini Tutorial

Handover Switching an on-going call to a different channel or cell in a wireless cellular network. Also known as "handoff."
Harmonic Distortion

Harmonic distortion is the presence of frequencies in the output of a device that are not present in the input signal, and are multiples of components of the input signal.

Clipping is a common cause but other nonlinearities can also introduce harmonics.

HART Highway Addressable Remote Transducer (HART) communication is a commonly used mode of transmission for digital signals that are superimposed on the analog signal of a 4–20mA current loop.

The HART protocol is based on the phase continuous frequency shift keying (FSK) technique. Bit 0 is modulated to a 2200Hz sinusoidal signal, and bit 1 is modulated to a 1200Hz sinusoidal signal with a baud rate of 1200bps. These two frequencies can easily be superimposed on the analog current-loop signal, which is in the range of DC to 10Hz, without affecting either signal. This unique nature of the HART protocol enables simultaneous analog and digital communication on the same wire.

HAST Highly accelerated stress test; highly accelerated steam and temperature
HB LED High-Brightness LEDs are any of a new generation of LEDs bright enough for illumination applications such as automotive interior, exterior, and display; room and architectural illumination; task and general lighting; projection display; display backlights; and signage.

See: High-Brightness LED Drivers and Solutions

HBT Heterojunction bipolar transistor
HD Harmonic distortion
HDLC High Level Data Link Control: An ITU-TSS link layer protocol standard for point-to-point and multi-point communications.
HDSL High bit-rate Digital Subscriber Line: The oldest of the DSL technologies, it continues to be used by telephone companies deploying T1 lines at 1.5Mbps and requires two twisted pairs.
HDTV High-definition television: an all-digital system for transmitting a TV signal with far greater resolution than the analog standards (PAL, NTSC, and SECAM). A high-definition television set can display several resolutions, (up to two million pixels versus a common television set's 360,000). HDTV offers other advantages such as greatly improved color encoding and the loss-free reproduction inherent in digital technologies.
Heat Sink Mechanical device that is thermally-connected to a heat-producing electronic component, designed to conduct heat away from the device. Most heat sinks are aluminum and employ fins to increase surface area and encourage the transfer of heat to the ambient environment.
HEMT High-electron-mobility transistor
HF High frequency
HGLL High gain, low linearity

Hi-Z (or High-Z or high impedance) refers to an output signal state in which the signal is not being driven. The signal is left open, so that another output pin (e.g. elsewhere on a bus) can drive the signal or the signal level can be determined by a passive device (typically, a pull-up resistor).

See Also:

High-Side An element connected between the supply and the load. High-side current sensing applications measure current by looking at the voltage drop across a resistor placed between the supply and the load.
Home RF Trademarked name for Home Radio Frequency, a networking technology which uses antennae and transmitters to provide wireless home networking via transmitted radio signals.
HomePlug HomePlug (Powerline) is an industry-standard method for transmitting data via the power lines. It can transmit audio, video, control signals, etc. HomePlug is a trademark of the HomePlug Powerline Alliance; Powerline is the generic term for the method.

See our Powerline product page.

PLC is an acronym for Powerline Communications.
Hot-Swap A power supply line controller which allows circuit boards or other devices to be removed and replaced while the system remains powered up. Hotswap devices typically protect against overvoltage, undervoltage, and inrush current that can cause faults, errors, and hardware damage.
HR High reliability
HSDPA High-Speed Downlink Packet Access (HSDPA) is a 3G radio interface standard in the HSPA family for wireless and cellular handsets or datacards that increase the datarate and improve the traffic handling of existing UMTS standards.
HSPA High-Speed Packet Access (HSPA) is a collection of radio interface standards for wireless and cellular handsets or datacards that increase the datarate and improve the traffic handling of existing UMTS standards.
HSSI High-Speed Serial Interface: A short-distance communications standard for data rates from 2Mbps to 52Mbps.
HSUPA High-Speed Uplink Packet Access (HSUPA) is a 3G radio interface standard in the HSPA family for wireless and cellular handsets or datacards that increase the datarate and improve the traffic handling of existing UMTS standards.
HTML Hyper Text Markup Language: Coding language used to create web pages.
HTS High-temperature semiconductor
HTTP Hyper Text Transport/transfer Protocol
Human Body Model

The human body model is an ESD test method where the ESD generator consists of a 100pF capacitor and a 1.5kohm series resistor.

See our application notes that describe how ESD is generated, how it damages electronic systems, human body and machine models for testing, IEC compliance levels, and design approaches.

Learn More:

See Also: Air Discharge

HVAC Heating, Ventilation, and Air Conditioning: Industry term for the systems and technology responsible for the heating, ventilation, and air conditioning in buildings. HVAC systems regulate comfort (temperature and humidity), energy efficiency, and air quality.

Hz Hertz: A measure of frequency. An older term is cycles per second, or cps.

I²C (pronounced "I-squared-C" and typeset as I²C but often typed as I2C) is short for "inter-IC bus." I²C is a two-wire, low-speed, serial data connection IC bus used to run signals between integrated circuits, generally on the same board.

SMBus™ is electrically similar.

Learn More:

I²S Inter-IC Sound (I²S) is an electrical bus interface standard used for connecting digital audio devices. The I²S bus separates clock and data signals, resulting in a very low-jitter connection. The bus consists of three lines: a clock line, a word-select line, and a multiplexed-data line.
I/O Input/output
I/Q 1. I/Q modulation is a method for combining two channels of information into one signal so that they can be separated at a later stage. Two quadrature carriers, 90 degrees out of phase, are modulated, then combined.

Abbreviated from "in-phase/quadrature-phase" which refers to the two carrier signals' phase relationship.

2. IQ (Q should be subscripted but sometimes printed as "IQ" without subscripting): Quiescent current: The current consumed when a circuit is in a quiet state, driving no load and if appropriate, with its inputs not cycling.

3. Intelligence quotient, a measure in which electrical engineers invariably excel.

IBO Input Back-Off: In a power amplifier, a measure of how far you must reduce the input power in order to receive the desired output linearity and power. Stated differently, the ratio between the input power that delivers maximum power to the input power that delivers the desired linearity.
IC 1. Integrated circuit: A semiconductor device that combines multiple transistors and other components and interconnects on a single piece of semiconductor material.

2. Internally Connected

ICA Integrated circuit accumulator
ICR Internal calibration register
Ideality Factor A constant adjustment factor used to correct for discrepancies between an ideal PN junction equation and a measured device.
Idle Mode™ A method for improving the efficiency of switching regulators by skipping pulses when the circuit is lightly loaded.

This variation in PWM (pulse-width modulation) combines the efficiency at low loads afforded by PFM (Pulse-Frequency Modulation) with PWM's efficiency and low-noise characteristics at higher loads. At light loads the circuit skips pulses as necessary (acting like a PFM circuit). At higher loads it acts like PWM. The net result is the maximum efficiency over the widest possible load range.

Learn more: "DC-DC Converter Tutorial" (see the paragraphs around Figure 14).

IEC 1. IEC stands for the International Electrotechnical Commission: An "organization that prepares and publishes international standards for all electrical, electronic and related technologies."

2. Commonly used to refer to one of the 13 power connectors described by specification IEC 60320. Most commonly refers to the C13 and C14 connectors used by most computers and many AC-powered electronic devices to connect the AC power.

3. Integrated electronic component.

IEEE From "The IEEE (Eye-triple-E) is a non-profit, technical professional association of more than 360,000 individual members in approximately 175 countries. The full name is the Institute of Electrical and Electronics Engineers, Inc., although the organization is most popularly known and referred to by the letters I-E-E-E." IEEE also sponsors many electrical and electronic standards.
IERC International Electronic Research Corp
IF Intermediate Frequency: Radio communications systems modulate a carrier frequency with a baseband signal in order to achieve radio transmission. In many cases, the carrier is not modulated directly. Instead, a lower IF signal is modulated and processed. At a later circuit stage, the IF signal is converted up to the transmission frequency band.
IFM ISDN file manager
IFT Intermediate-frequency transform

Third Order Input Intercept Point (IIP3) is the point at which the power in the third-order product and the fundamental tone intersect, when the amplifier is assumed to be linear. IIP3 is a very useful parameter to predict low-level intermodulation effects.

IMA Inverse Multiplexing over ATM, an MGX card module that supports T3 or E3 inverse multiplexing on up to eight T1 or E1 lines.
Image Frequency Receivers typically convert RF signals to a lower Intermediate Frequency (IF) for demodulation. In addition to the IF, a second signal, called the "image frequency" is often generated and filtered out.
Image Rejection The measure of a receiver's ability to reject signals at its image frequency. It is normally expressed as the ratio, in dB, of the receiver's sensitivity at the desired frequency versus the sensitivity at the image frequency.

Intermodulation Distortion (IMD): When two signals mix in non-linear circuits or devices, new frequency components are created that are not in the original signal. The resulting signal error is called intermodulation distortion, or IMD.

Impedance Impedance, represented by the symbol Z, is a measure of the opposition to electrical flow. It is measured in ohms.

For DC systems, impedance and resistance are the same, defined as the voltage across an element divided by the current (R = V/I).

In AC systems, the "reactance" enters the equation due to the frequency-dependent contributions of capacitance and inductance. Impedance in an AC system is still measured in ohms and represented by the equation Z = V/I, but V and I are frequency-dependent.

Impedance equations

See also: Impedance matching

Impedance Matching

Impedance matching is designing source and load impedances to minimize signal reflection or maximize power transfer. In DC circuits, the source and load should be equal. In AC circuits, the source should either equal the load or the complex conjugate of the load, depending on the goal.

Impedance (Z) is a measure of the opposition to electrical flow, which is a complex value with the real part being defined as the resistance (R), and the imaginary part is called the reactance (X). The equation for impedance is then by definition Z=R+jX, where j is the imaginary unit. In DC systems, the reactance is zero, so the impedance is the same as the resistance.

Why is impedance matching needed?

Impedance mismatch can lead to signal reflection and inefficient power transfer. These reflections cause destructive interference, leading to peaks and valleys in the voltage. Impedance matching is therefore important to obtain a desirable VSWR (voltage standing wave ratio).

Conjugate matching vs. reflectionless matching

Depending on whether the goal of impedance matching is maximizing power transfer or minimizing signal refection, either conjugate matching or reflectionless matching is required.

Maximum power transfer is obtained when the output impedance of the source is equal to the complex conjugate of the input impedance of the load (ZS=RL-jXL). This is called conjugate matching.

Minimal signal reflection is obtained when the source impedance is equal to the load impedance (ZS=RL+jXL), which is called reflectionless matching.

Since reactance is zero in DC systems, this is equivalent to the two resistances being the same in either case. Impedance matching will result in both minimal signal reflection and maximal power transfer in DC systems.

What is an impedance matching device?

Matching networks are configurations used to match source and load impedances, and impedance matching devices are the components that make up these networks. Finding these component values can be done using computer simulations, manual computations, or with tools such as the Smith chart.

Smith Chart for impedance matching

Smith Chart for impedance matching.

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IMVP Intel Mobile Voltage Positioning: A technology in which the processor voltage (VCC) is dynamically adjusted, based on the processor activity, to reduce processor power. It allows higher processor clock speed at a given power consumption; or lower consumption at a given clock frequency.
Inductive Kickback

Inductive kickback is the very rapid change in voltage across an inductor when current flow is interrupted.

Snubber diodes are often used to channel this energy in relays, and other inductive loads. Kickback can be a problem (causing EMI and component failure); or it can be used in power supply circuits to develop higher or opposite-polarity voltages from a single supply.

InfiniBand InfiniBand architecture is an industry standard, channel-based, switched-fabric, interconnect architecture for servers. InfiniBand architecture changes the way servers are built, deployed, and managed.
InGaAs Indium gallium arsenide
Ingress Protection An Ingress Protection (IP) rating indicates how well an enclosure is protected from penetration by contaminants such as dust or fluids (such as water). IP ratings are defined in the IEC standard 60529.

See also:

INL Integral nonlinearity
Input CMVR (V) Common-mode voltage range (CMVR) or Input Voltage Range (IVR): For signal processing devices with differential inputs, such as an op amp, CMVR is the range of common mode signal for which the amplifier's operation remains linear.

If we let the voltage present on the "-" input equal V1, and the voltage on the "+" input equal V2, then the common mode voltage is VCM = (V1+V2)/2.

Some op amps, for instance, will only allow the common mode voltage of a signal to come within a diode drop or so of the power supply rails. Many of Maxim's op amps will allow the common mode input voltage to go all the way to one or both supply rails. Some even allow inputs beyond the supply rails (Beyond-The-Rails™).

Inrush Current A momentary input current surge, measured during the initial turn-on of the power supply. This current reduces to a lower steady-state current once the input capacitors charge. Hotswap controllers or other forms of protection are often used to limit inrush current, because uncontrolled inrush can damage components, lower the available supply voltage to other circuits, and cause system errors.
Int. Ref. Internal Reference. An on-chip voltage reference.
Integral Nonlinearity A measure of a data converter's ability to adhere to an ideal slope in its transfer function. It can be specified using end-point or best-straight-line fit. Each of these approaches can yield very different numbers for the same data converter.
Integrated Heat Spreader An Integrated Heat Spreader (IHS) is the surface used to make contact between a heatsink or other thermal solution and a CPU or GPU processor.
Intellectual Property Intellectual Property: Creations of the intellect such as trade knowledge, technical information, and literary or artistic work, including patents, copyrights, and trademarks.
Interleave To organize the data sectors on a computer hard disk, so the read/write heads can access information faster.

Intermodulation is a process whereby signals mix together in a circuit and nonlinearities in the circuit create undesired output frequencies that are not present at the input.

See Also:

Internet Protocol Standard method for data transfer used on the Internet. Also known as IP or TCP/IP.
Inverting Op Amp

An inverting op amp is an operational amplifier circuit with an output voltage that changes in the opposite direction as the input voltage. In other words, it is out of phase by 180o

What is an inverting input?

An amplifier’s inverting input refers to the pin configuration. The inverting input is the terminal marked with a minus (-) sign, and the non-inverting input is marked with a plus (+) sign. These can also be referred to as negative and positive terminals.

Circuit diagram symbol for an op amp with inverting and non-inverting inputs.

Circuit diagram symbol for an op amp with inverting (-) and non-inverting (+) inputs.

How do inverting op amps work?

Inverting op amps work following the op amp golden rules:

  1. The Current Rule: No current flows into the inputs of the op amp. (I+=I-=0)
  2. The Voltage Rule: The output of the op amp attempts to ensure that the voltage difference between the two inputs is zero (V+=V-)

Inverting op amp circuit.

Inverting op amp circuit.

Consider the inverting op amp circuit shown above. Since the inverting input is tied to ground, by the Voltage Rule, the non-inverting input must also be at (virtual) ground.

The current flowing through R1 is I=Vin/R1,and since the Current Rule states that the inputs draw no current, all of that current must then flow through R2.

Since the inverting input is at virtual ground, the output of the inverting op amp is Vout=-IR2=-VinR2/R1.

This makes the gain of the inverting op amp circuit -R2/R1.The gain is negative, meaning the output is out of phase with the input.

Op amp inverter

An op amp inverter is an inverting buffer constructed with an operational amplifier. An inverting buffer changes the direction of the signal without amplifying it, so the gain of the circuit is -1. We can see above that the inverting op amp circuit has a gain of -1 when the two resistors are equal, so an op amp inverter is an inverting op amp with R1=R2.

Learn More: Operational Amplifiers (Op Amps)

See Also: Non-Inverting Op Amp

Inverting Switching Regulator A switch-mode voltage regulator in which output voltage is negative with respect to its input voltage.

See application note 660, "Regulator topologies for battery-powered systems."

IO-Link is a 24-volt, three-wire, half-duplex, point-to-point sensor and actuator communication interface. Remote configuration, diagnostics, event triggering and process data readout are made possible from a PLC via a three layer protocol stack. IO-Link can be used for simple binary sensors and smart sensors.

Learn More:


Third-order intercept point

Learn More: IP3 and Intermodulation Guide

IR Infrared: Light that has a frequency below the visible light spectrum, used for remote controls, line-of-sight wireless data, and night vision applications, among others.
IrDA Infrared Data Association: A group of device manufacturers that developed a standard for transmitting data via infrared light waves.
IRE Institute of Radio Engineers; IREs are units of measurement dividing the area from the bottom of sync to peak white level into 140 equal units. 140 IRE = 1VP-P
IRO Input-referred offset
IRS Interface register set
IRSA Interface register set address
IRSD Interface register set data
IS IN SEL (control bit)
ISA Industry-standard architecture
ISI Inter-Symbol Interference: A form of interference that occurs when echoes of a radio-signal interfere with the original signal. ISI can reduce the effective data rate of wireless LAN transceivers.
ISM Industrial, Scientific and Medical: Radio frequency bands made available for use by communication equipment without license, within certain maximum emitted power limits. Equipment which uses the ISM band must tolerate interference from other such equipment. Common uses include WiFi (802.11a, b, and g) and cordless phones.
ISO International Standards Organization
ISP Internet Service Provider: Company that offers connection to the Internet.
ITU International Telecommunication Union: An international organization under the UN that is concerned with telecommunications.
JALT Jitter attentuator limit trip
JBOD Just a Bunch of Disks: An array of hard disks without a controller.
JEDEC Joint Electron Device Engineering Council
JFET A JFET, or junction field-effect transistor, or JUGFET, is a FET in which the gate is created by reverse-biased junction (as opposed to the MOSFET which creates a junction via a field generated by conductive gate, separated from the gate region by a thin insulator).

For example: A p-channel JFET would consist of a bar of p-type silicon with the "drain" at one end and the "source" at the other. Between these two terminals is some n-type material connected to a "gate". A positive voltage applied to the gate creates a "depletion field" which restricts current flow between the source and drain.

JITT Just-in-time tester

Jitter is the slight movement of a transmission signal in time or phase that can introduce errors and loss of synchronization. Jitter may also be referred to as phase jitter, timing distortion, or intersymbol interference.

More jitter will be encountered with longer cables, cables with higher attenuation, and signals at higher data rates.

Learn More:

Joule Joule (abbreviated J): A measurement of energy or work. In mechanical systems, it's the a force of one newton, moving an object a distance of one meter.

In electronics, it's the same amount of energy, in electrical units. One joule is one watt of power, applied for one second (a watt-second); or a coulomb of electrical charge raised to a potential of one volt.

JPEG Joint Photography Experts Group; more commonly, files that are compressed using the JPEG standard.
Junction Diode Sensor The use of a PN junction on a silicon die for determining die temperature.
JVM Java virtual machine.
k 1. Kilo: Metric unit representing 1000. E.g.: 1kHz is a 1 kilohertz (1000 Hertz). Note that the k is always lowercase.

In digital systems, "K" or "k" is often used to mean 210, that is, 1024. This is not well-standardized but it's usually apparent from context. On the Maxim site, we use upper-case K to mean 1024 and lower-case k to mean 1000. This standard is applied to new documents but older documents may use "k".

2. Kelvin: Temperature scale. Zero K is defined as absolute zero. 273.15K is 0 degrees C.

Note that temperatures on the kelvin scale are called kelvins, not "degrees kelvin." The K symbol is uppercase and used without a degree symbol. The word "kelvin" in this context is not capitalized.

Kanal+ Kanal+ support allows a VCR to record audio and video signals captured by both the set top box (STB) and the television, without changing SCART connections on the back of the TV, STB, and VCR.

See: Application note 4522, "Low-Cost, Dual SCART Solution for Set-Top Boxes Also Has Optional Kanal+ Support."

kb Kilobit(s)
Keep-Out Zone The area on or near a CPU or GPU processor that the circuit board layout design can not use, due to thermal management components, cooling, and mounting constraints.
kg Kilogram(s)
kHz Kilohertz
km Kilometer(s)
kVM Keyboard Video Mouse: Defacto standard for the three cables used on a typical cpr: One for the keyboard; one for the monitor (video); one for the mouse. Also: A KVM switch is a switch box used to connect one KVM to multiple computers.
kW Kilowatt (or kilowatts): 1000 watts.

kWh Kilowatt hour(s)
L-Band The group of radio frequencies extending from 390MHz to 1550MHz. The GPS carrier frequencies (1227.6MHz and 1575.42MHz) are in the L-band.
LAN Local Area Network: A computer network, usually within one building, that connects computers, file and mail servers, storage, peripherals, and other devices in a way that permits data interchange and sharing of resources. Ethernet and WiFi (802.11) are common examples.
Laser Driver An IC that supplies modulated current to a laser diode in response to an input serial-data stream.
LCC 1. Leadless Ceramic Chip Carrier or Leadless Chip Carrier: An IC package, usually ceramic, that has no leads (pins). It instead uses metal pads at its outer edge to make contact with the printed circuit board. Example: Maxim 20-pin LCC diagram (PDF)

2. Leaded Chip Carrier, also called PLCC or Plastic Leaded Chip Carrier: A square surface mount chip package in plastic with leads (pins) on all four sides. Example: Maxim 20-pin PLCC diagram (PDF)

LCD Liquid-crystal display

Low Drop Out: A linear voltage regulator that will operate even when the input voltage barely exceeds the desired output voltage.

Learn More: Linear Regulators (LDOs)

Leakage Inductance

Leakage inductance in a transformer is an inductive component that results from the imperfect magnetic linking of one winding to another.

In an ideal transformer, 100% of the energy is magnetically coupled from the primary to the secondary windings. Imperfect coupling reduces the signal induced in the secondary windings. The electrical equivalent is some self-inductance in series with the primary windings that are properly coupled. This series inductance is the "leakage inductance."

LED Light-Emitting Diode: A semiconductor device that emits light (usually visible or infrared) when forward-biased.

The application note, "Driving LEDs in Battery-Operated Applications: Controlling Brightness Power Efficiently" has a good explanation of how LEDs work, especially with regard to current vs. LED brightness and schemes for matching brightness when driving multiple LEDs.

Level Translator

A level translator is a device which translates a logic signal from one type to another, for example, ECL to TTL.

Learn More: Level Translators


A linear Feedback Shift Register is a shift register in which some of its outputs are connected to the input through some logic gates (typically, an XOR).

A wide variety of bit patterns can be generated inexpensively, including pseudo-random sequences. Can be used as a noise generator.

Learn More:

LGHL Low gain, high linearity

LiDAR (light detection and ranging) is a remote sensing method that uses laser beams to create a 3D scan of the surrounding area. LiDAR is an important means of proximity sensing in autonomous vehicles.

What is LiDAR and how does it work?

LiDAR works by emitting pulses of laser light and measuring the return time between the emitted signal and the signal that is reflected after bouncing off of a nearby object. Since LiDAR uses light signals, the distance to the object is easily calculated by multiplying the time of flight by the speed of light. The use of light also makes for very quick return times.

The distance map shows the objects detected by a LiDAR laser/receiver system.

The distance map in (B) shows the objects detected in (A) by a LiDAR laser/receiver system. The closest object (in red) has the shortest time of flight, while the farthest (in green) has the longest.

By continually emitting these short laser bursts, and in multiple directions, the system can create a distance map of all of the surrounding objects that updates instantly and continuously.

Autonomous vehicles emitting LiDAR signals.

Illustration of autonomous vehicles emitting LiDAR signals in multiple directions to detect objects on the road.

How does a LiDAR laser/receiver system work?

LiDAR block diagram.

The block diagram above shows a typical operating circuit. The laser driver initiates the light pulse towards the object, and the returned signal reflects into the photodiode D1 which converts the light to current. The transimpedance amplifier TIA1 converts the current to voltage and amplifies the signal to then be sent to the comparator COMP1, which converts the analog signal to a digital one. The D2/TIA2/COMP2 system works similarly to record the initial signal, and all of this information is processed and stored by the MCU.

LiDAR vs. radar

LiDAR and radar are similar in that they both measure time of flight to determine distance from an object, and the difference is what type of signal they use. Where LiDAR is Light Detection and Ranging, radar is Radio Detection and Ranging, and these are the types of waves that each system emits. Light waves are in the nm to μm wavelength range, where radio waves are in the cm to km wavelength range.

Comparison of LiDAR, radar, and cameras.

LiDAR’s smaller wavelengths make it able to create more precise and accurate distance maps, detecting smaller objects and greater detail. Radar’s longer wavelength range makes it less sensitive to changes in the medium through which it travels (such as poor weather). Because of these differences, the two are often used together (sometimes with cameras) to form vision and driving capabilities that exceed those of humans.

Learn More:

Related Parts:

Light Sensor

Light sensors are a type of photodetector (also called photosensors) that detect light. Different types of light sensors can be used to measure illuminance, respond to changes in the amount of light received, or convert light to electricity.

What are the different types of light sensors?

Common types of light sensors are photodiodes, photoresistors, phototransistors, and photovoltaic light sensors. These components can be used in applications such as light sensing in mobile devices, automatic outdoor lighting, proximity sensors, and renewable energy.

Photodiodes convert light into an electrical current. They are p-n junction devices that are similar to normal diodes. A p-n junction device consists of a p-type and an n-type semiconducting material. The “p” stands for “positive” due to the material’s excess of electron holes, and the “n” stands for “negative” due to an excess of electrons. This means that current can only flow in one direction through the boundary. In a photodiode, these electron hole pairs are formed when the energy from the incident light is absorbed by the device. Also see the related term avalanche photodiode.

Photoresistors (also known as light-dependent resistors or LDRs) are passive devices that decrease resistance in proportion to the amount of light received. Light forming electron hole pairs increases conductivity and therefore decreases resistivity.

Phototransistors switch or amplify signals similarly to regular transistors, with the current applied to the terminals being created from exposure to light.

Photovoltaic (or solar cells) convert light into electricity in a process known as energy harvesting. Voltage and electric current are generated by way of the photovoltaic effect exhibited by the cell's semiconducting components.

How do light sensors work?

Light sensors work by the photoelectric effect. Light can behave as a particle, referred to as a photon. When a photon hits the metal surface of the light sensor, the energy of the light is absorbed by the electrons, increasing their kinetic energy and allowing them to be emitted from the material. This movement of electrons, and therefore charge, is electrical current.

The photovoltaic effect is similar to the photoelectric effect in that the light is absorbed by electrons, causing them to be in a higher-energy state. In the photoelectric effect, the electrons are ejected from the material completely. In the photovoltaic effect, the electrons are excited from the valence band into the conduction band, but remain within the same material.

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LIN Local Interconnect Network (LIN): Defined by the LIN-BUS consortium, a LIN is a low data-rate, single-wire communications system, used in automotive and heavy vehicle applications.
Line Regulation The ability of a power-supply voltage regulator to maintain its output voltage despite variations in its input voltage.
Linear 1. Having the property that the output is proportional to the input. E.g.:

  VOUT = k*VIN

where k is a constant.

2. Analog; as in a "linear" circuit (as opposed to digital).

Linear Mode Uses a linear-pass element (BJT or FET) to control/regulate the charging voltage/current.
Linear Regulator

A voltage regulator that is placed between a supply and the load and provides a constant voltage by varying its effective resistance.

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Lithium batteries Lithium batteries for low-power, high-reliability, long-life applications such as non-volatile memory and timekeeping (typically in coin-shaped cells) use a variety of lithium-based chemistries (as differentiated from lithium-ion).

Maxim NV SRAM and timekeeping products use mostly BR chemistry (poly-carbonmonofluoride) primary (non-rechargeable) lithium coin cells. We use CR chemistry (manganese dioxide) primary lithium coin cells in microcontroller and touch products. Some new products use "manganese lithium" (ML) chemistry, which is chemically close to the CR, but is a secondary (rechargeable) lithium coin cell.
Lithium-ion batteries Lithium and lithium-ion: A number of battery chemistries are based on the element lithium, a highly-reactive metallic element. Lithium-based batteries are common in two applications: Power for portable equipment such as cell phones, laptops, and MP3 players; and low-power, long-life applications such as powering memory elements and clocks.

Lithium-ion (Li+, Li-Ion, Lion) cells are generally used as power sources for portable equipment. They are usually rechargeable. Lithium-ion and nickel-metal-hydride (NiMH) have displaced nickel-cadmium (NiCd or nicad) as the dominant rechargeable chemistry for portable applications. Maxim makes a wide range of battery management products for all these families, including chargers, fuel gauges, and smart battery components.

Lithium batteries are typically coin-shaped and are used to power items such as Maxim's non-volatile static RAM (NV SRAM) and timekeeping circuits (such as real-time clocks).

Also see:

LL Local loopback
Lm Lumen(s)
Lm/W Lumen(s) per watt
LMDS Local Multipoint Distribution Service: A broadband radio service, located in the 28GHz and 31GHz bands, designed to provide two-way transmission of voice, high-speed data and video (wireless cable TV). In the U.S., FCC rules prohibit incumbent local exchange carriers and cable-TV companies from offering in-region LMDS.
LNA Low noise amplifier. Typical use: The first stage of a satellite receiver.
LO Local oscillator
Load Regulation Load regulation refers to circuitry that compensates for changes in load. Most commonly: Circuits that keep voltage constant as load varies.
Local Temperature

Local temperature is the temperature measured on the die of the temperature-measuring integrated circuit.

See Also:

Local Temperature Sensor

A local temperature sensor is an element or function of an integrated circuit that measures its own die temperature.

See Also:

LOL Loss of lock
Long Haul A network that spans distances larger than a local area network (LAN). Because electrical and optical transmissions fade over distance, long-haul networks are difficult and expensive to implement.
Long Term Evolution LTE (Long Term Evolution) is a high-speed mobile communications cellular standard developed by the 3rd Generation Partnership Project (3GPP). LTE is an evolution of GSM/UMTS standards.
LOP Loss of power
LOS Loss of signal
Low Batt. Det. Low battery detector
Low Line O/P Low line output
Low-Pass Filter

A low-pass filter (LPF) is a circuit that only passes signals below its cutoff frequency while attenuating all signals above it. It is the complement of a high-pass filter, which only passes signals above its cutoff frequency and attenuates all signals below it.

What is a low-pass filter used for?

Low-pass filters have applications such as anti-aliasing, reconstruction, and speech processing, and can be used in audio amplifiers, equalizers, and speakers.

Low-pass filters can also be used in conjunction with high-pass filters to form bandpass, band-stop, and notch filters. A bandpass filter passes a range of frequencies while attenuating all frequencies outside of the band. A band-stop filter (also called a band reject filter) does the opposite, attenuating signals within its stopband while passing all frequencies outside of it. Notch filters are a type of band-stop filter that attenuate a very narrow set of frequencies, which can be created from a combination of low-pass and high-pass filters with cutoff frequencies very close to each other.

What is a low-pass filter circuit?

There are many different low-pass filter circuits, which are characterized by their order and amplitude characteristic or the type of polynomial that describes it (Butterworth, Chebyshev, Elliptic, or Bessel):

Butterworth - response that is flat in the passband and an adequate rate of rolloff.

Chebyshev - frequency cutoff is steeper than that of a Butterworth, at the cost of a variation in amplitude known as ripple in the passband.

Elliptic (or Cauer) - compared to the Chebyshev, the stopband cutoff is sharper (without incurring more passband ripple), but transient response is worse.

Bessel - represents a trade-off in the opposite direction from the Butterworth. Transient response is improved, but at the expense of a less steep cutoff in the stopband.

Amplitude and group delay vs. frequency for various filter types normalized to a 1-rad bandwidth.

Amplitude and group delay vs. frequency for various filter types normalized to a 1-rad bandwidth.

For more on first and second order filters, as well as Butterworth, Chebyshev, Elliptic, and Bessel filters, see Tutorial 733: A Filter Primer.

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Low-Side An element connected between the load and ground. Low-side current sensing applications measure current by looking at the voltage drop across a resistor placed between the load and ground.
LSB Least-significant bit. In a binary number, the LSB is the least weighted bit in the number. Typically, binary numbers are written with the MSB in the left-most position; the LSB is the furthest-right bit.
LSI Large-scale integration (LSI). See VLSI.

1. The emitted light, projected per unit area, measured in cd/m2 (candela per square meter). Often incorrectly equated with "brightness".

2. The black and white portion of a video signal, also referred to as the "Y" component. A composite, Y/C, or Y/Pb/Pr video signal combines a luminance signal with color components.

LVC Lowest voltage clamp
LVDS Low Voltage Differential Signaling
LVECL Low Voltage Emitter Coupled Logic
LVPECL Low Voltage Positive Emitter Coupled Logic
LVS Layout versus schematic
LVTTL Low Voltage Transistor-Transistor Logic
M2M Machine-to-machine or machine-to-mobile communications, via wireless technologies such as cell phone network technologies, WLAN, Bluetooth, and RFID (radio frequency identification). Applications include automatic meter reading, fleet management, vending, monitoring and control, security and alarms, and telemedicine.
mA Milliampere, or milliamp: 1/1000 of an Ampere. Ampere is the basic unit for measuring electrical current.

What is a Milliampere Equal To?

The “Ampere”, usually abbreviated as “Amp” in spoken language, is the SI unit of electrical current and has the written symbol A. Electronic components usually use currents that are less than 1 Amp. Engineers use engineering notation (a subset of scientific notation) to avoid using fractions. Instead of using terms like 0.5 Amps or 0.01 Amps, it is more convenient to express small currents as multiples of “milliAmps”.

One milliAmp is equivalent is one thousandth of an Amp. For example, 0.1 Amps is equivalent to 100 milliAmps and 0.01 Amps is 10 milliAmps. While the term “milliAmp” is used in spoken communication, it is abbreviated as mA in writing. A Light Emitting Diode or LED (Figure 1) typically used to indicate if a piece of equipment is switched on or in standby will normally use between 10 and 30 milliAmps.
Figure 1. LED standby indicator

What is a microAmpere?

A microAmpere (usually abbreviated as microAmp in spoken language) is one thousandth of a milliAmp or 1 millionth of an Amp. 1 microAmp is abbreviated in writing as 1 µA. The symbol “µ” (pronounced “mew”) is from the Greek Alphabet. As electronic components have shrunk in size, the amount of current they use has also got smaller, even less than 1 mA. Currents that are smaller than 1mA are usually referred to in multiples of microAmps. For example, 0.1 mA is equivalent to 100 µA. Electronic components that use currents less than 1mA are often referred to as microelectronic components or devices. An example would be a single transistor on a silicon chip. The symbol for a transistor is shown in Figure 2.
Figure 2. Transistor Symbol

What Does Milliampere Stand For?

The term milliAmp is commonly used when specifying the capacity of a battery. For example, the capacity of a mobile phone battery (Figure 3) might be 3000 milliAmp – hours (written as 3000 mAh). This means the battery can supply 3000 mA for 1 hour or 6000 mA for 30 minutes or 1000mA for three hours etc. In other words, the more current that is used by the phone, the shorter the length of time the battery will last.
Figure 3. 3000mAh Mobile Phone Battery

What is the Meaning of mA in Electricity?

Electricity companies charge customers for electricity by the amount of current they use called “units”. One unit of electricity is 1 kilowatt-hour (in the U.S, this equates to approximately 10 Amps per hour). The number of units used is recorded on an electricity meter (Figure 4). Readings are made, usually monthly or bimonthly, and consumers are then billed for their usage.
Figure 4. Electricity Meter
MAC Address Media Access Control Address (maca, MAC): A hardware address that uniquely identifies each node of a network, as in IEEE-802 (Ethernet) networks. The MAC layer interfaces directly with the network medium.
Manchester Data Encoding Manchester encoding is a form of binary phase-shift keying (BPSK) that has gained wide acceptance as a modulation scheme for low-cost radio-frequency (RF) transmission of digital data. Its key characteristic is that it encodes data in a way that insures there will never be long strings of continuous zeros or ones. The guaranteed transitions means that the clock can be derived from the transmitted data, allowing the link to function with variable signal strengths from transmitters with imprecise, low-cost, data-rate clocks.

Details: See the application note, Manchester Data Encoding for Radio Communications.

MAP Manifold absolute pressure
Margining Margining is a test procedure that determines the "safety margin." A parameter is varied to determine the device's sensitivity or ability to perform given a range of inputs. A large number of parts can be characterized to determine a safe range for the specification, to guarantee performance and yield.
Max. DNL (LSB) Maximum differential nonlinearly expressed in least significant bit(s).
Max. Hold Step (MV) When switching between sample mode and hold mode, charge injection from stray capacitance causes the maximum voltage of the hold capacitor to change.
Max. INL as percent FSR "Max. INL (±%FSR)" is the maximum integral nonlinearity, expressed as a percentage of full-scale range.
MAXTON Maximum time-on

Make-before-break: In a switching device, a configuration in which the new connection path is established before the previous contacts are opened. This prevents the switched path from ever seeing an open circuit.

Applies to mechanical systems (e.g. that use relays or manual switches) and to solid-state analog multiplexers and switches.

Learn More: Switches and Multiplexers

MBC Main booster converter
MC Multicommunicator
  1. Multi-Chip Module (MCM): An integrated circuit package that contains two or more interconnected chips.
  2. MCM is an abbreviation for thousands of circular mils, an old measurement of wire gauge. 1 MCM = 1 kcmil = 0.5067 square milimeters. A mil is 1/1000 inch. A wire 200 mils in diameter is 40 MCM.
  3. MCM is generally used for very large-diameter wire. Most wire uses AWG.
  4. MCM is also used for "million cubic meters."
Mcps 1. Megacycles per second (obsolete): Megahertz

2. Megachips per Second (Mcps): In a Direct-Sequence Spread Spectrum signal, a "chip" is an encoding element. Mcps is a measure of the speed at which chips can be generated by a circuit.

See: "An Introduction to Spread-Spectrum Communications."

MDAC Multiplying digital-to-analog converter
Media Independent Interface A parallel digital bus used for 10Mbps and 100Mbps Ethernet.
MegaBaud RS-232 logic-level compatible data rates that are 1Mbps or higher.
MEMS Acronym for "Micro Electronic Mechanical Systems," or microelectromechanical systems: Systems that combine mechanical and electrical components and are fabricated using semiconductor fabrication techniques. Common examples are pressure and acceleration sensors which combine the sensor and amplification or conditioning circuitry. Other applications include switches, valves, and waveguides.
MESFET A Metal-Semiconductor Field-Effect-Transistor uses a metal-semiconductor (Schottky) junction to create the conductive channel, rather than using a p-n junction as a JFET does; or a metal-oxide-semiconductor layer as a MOSFET uses.
Metal Oxide Varistor A Metal Oxide Varistor (MOV, or surge-suppressor) is a discrete electronic component that diverts excessive voltage to the ground and/or neutral lines.
MFSK Multiple frequency-shift keying
MHz Megahertz (MHz): Measurement of frequency -- million cycles per second.
Micro Energy Cell A Micro Energy Cell (MEC) is a small, rechargeable, very long life, energy storage device used in energy harvesting applications.

An example is the THINERGY® MEC from Infinite Power Solutions.

MicroLAN A 1-Wire network. A low-cost network in which PCs or microcontrollers communicate digitally over twisted-pair cable using 1-Wire components.
MicroMonitor™ A device that monitors three conditions vital to processor-controlled systems: power supply, software execution, and external override.
Microprocessor Supervisor A device that monitors a host microprocessor or microcontroller's supply voltage and, in some cases, its activity. It monitors for a fault condition and takes appropriate action, usually issuing a reset to the microprocessor.
MIMO A Multiple Input, Multiple Output (MIMO) system has multiple antennas and multiple radios. It takes advantage of multipath effects, where a transmitted signal arrives at the receiver through a number of different paths. Each path can have a different time delay, and the result is that multiple instances of a single transmitted symbol arrive at the receiver at different times.

Usually multipath is a source of interference, but MIMO systems use the fact that data will arrive at the receiver at different times through different paths to improve the quality of the data link. For example, rather than relying on a single antenna path to receive an entire message, the message can be pieced together based on fragments received at the various antennas. This can act to either increase the data rate at a given range, or increase system range for a given data rate.

MIMO is used in the implementation of the 802.11n standard.

Min LOS Sens. The minimum sensitivity attainable with a programmable loss-of-signal feature.
Min Stable Closed Loop Gain The minimum closed-loop gain for which the amplifier is stable.
MISI Master-in, slave-out isolated input
MISO Master-in, slave-out isolated output

Mixed-signal ICs are integrated circuits that contain both analog and digital circuitry on one chip. An analog signal is a continuous time-varying signal, and a digital signal is a noncontinuous signal that takes on only a finite number of values. Mixed signal ICs make use of both of these types of signals. Mixed-signal ICs are used in a wide variety of applications and application-specific integrated circuits (ASICs).

Analog signals

As an example, a building block of analog circuit design is the op amp, which is a high-gain amplifier. An op amp can take a continuous signal and output another, higher-valued, continuous signal. An op amp can also be used to make a comparator, which is a circuit that compares two input voltages and outputs a binary signal indicating which is larger. Since the output of the comparator is digital, this is an example of a mixed-signal circuit.

Digital signals

Where analog signals are continuous, digital signals are discrete, meaning that they take on a finite number of values. An example is a square wave, where a signal alternates between values in steps, ideally instantaneously. Another example is a binary signal, which can have two possible values (such as 0/1 or on/off) and is used in logic gates such as AND/NAND gates or in D flip flops.

ADCs and DACs

The two clearest examples of mixed-signal ICs are analog to digital converters (ADCs) and digital to analog converters (DACs). Since these convert analog to digital or digital to analog, they must contain circuitry for both.

mm Millimeter(s)
MMI Man-machine interface

What is a Modulator?

A modulator is an electronic circuit that superimposes a low-frequency (information) signal onto a high-frequency (carrier) signal for the purpose of wireless transmission. The reason for this is that higher frequency signals can be received using shorter aerials, which are more practical than longer ones. The information signal can be either analog or digital.

The modulator circuit superimposes the information signal onto the carrier signal by modifying one of the properties of the carrier, i.e., amplitude, frequency, or phase.

The following table summarizes the main modulation types for each type of information signal.






Amplitude Modulation (AM)

Frequency Modulation


Phase Modulation



Amplitude Shift Keying


Frequency Shift Keying (FSK)

Phase Shift Keying


Once the transmitted signal has been detected and received, a demodulator circuit is then used to recover the information signal from the carrier. 

Learn MoreI/Q Modulators and Demodulators

Monotonic A sequence increases monotonically if for every n, Pn + 1 is greater than or equal to Pn. Similarly, a sequence decreases monotonically if for every n, Pn + 1 is less than or equal to Pn.

In plain language, the value rises and never falls; or it falls and never rises.


Metal-oxide semiconductor field-effect transistor; metal-oxide silicon field-effect transmitter.

In a MOSFET, the conductive channel between the drain and source contacts is controlled by a metal gate separated from the channel by a very thin insulating layer of oxide. The gate voltage establishes a field that allows or blocks current flow.

Compare to a JFET, in which a p-n junction controls the channel; or a MESFET, which uses a metal-semiconductor (Schottky) junction.

Learn More:

MOSI Master Out Slave In: One of the four Serial Peripheral Interface (SPI) pins.
MPU Microprocessing unit
MPW Multiproject wafer
MQFP Metric quad flat pack
mrad Milliradian(s)
ms Millisecond(s)
MSA Measurement Systems Analysis is a method for ensuring product test measurements are reliable, robust, and of good statistical merit.
MSB Most-significant bit. In a binary number, the MSB is the most weighted bit in the number. Typically, binary numbers are written with the MSB in the left-most position; the LSB is the furthest-right bit.

Megasamples per second: A measure of speed in digitizing systems, samples per second dictates the maximum frequencies that can be accurately captured.

See Also:

MTIMD Multitone intermodulation distortion
MTPR Multitone power ratio
Multipath In radio transmission, multipath refers to the simultaneous reception of two copies of the signal, that arrive via separate paths with different delays.

A common example is when a signal bounces off a building or other object and is received along with the direct (unbounced) signal. In television reception, this causes "ghosting" -- one sees a faded echo on the screen horizontally displaced from the main image.

Another common example is in radio (especially AM radio), where the signal bounces off the ionosphere and one receives that delayed signal along with the directly transmitted signal.

Usually, multipath is an undesired effect but in MIMO systems, separate antennas deliberately send replicas and sophisticated receivers piece together the fragments to improve performance.

Multiplex 1. Combining two signals (which can be analog or a digital stream) into one in such a way that they can later be separated. Examples are OFDM; standard FM stereo broadcast (in which left and right are multiplexed onto one baseband signal); standard television in which video and several audio signals shared the channel; and time-division multiplexing which gives each signal a separate time-slice.

2. An array of analog switches, usually on a single CMOS chip, that allows one input signal to be routed to any of several output lines, depending on the value of a set of digital control lines.

A multiplexer can also be used in the opposite direction, allowing the array to connect one of several input lines to the output, depending on the control lines.

Several of these can be implemented on one chip to make a multi-channel version.

Maxim makes hundreds of these parts. See the Analog Switch and Multiplexer Product Line page.

Murphy's Law Anything that can go wrong, will.
mV A millivolt (mV) is 1/1000 of a volt.
mW Milliwatt(s)
MW Megawatt(s)
MxTNI MxTNI™ (Maxim Tiny Network Interface, formerly called TINI) is Maxim's trademark for the industry's smallest web server. The MxTNI platform consists of a microcontroller that includes the facilities necessary to connect to the Internet. The platform is a combination of broad based I/O, a full TCP/IP stack and an extensible Java runtime environment that simplifies development of network-connected equipment.
nA Nanoampere(s)

NAND is an abbreviation for “NOT AND.”

What is a NAND gate?

A two-input NAND gate is a digital combination logic circuit that performs the logical inverse of an AND gate. While an AND gate outputs a logical “1” only if both inputs are logical “1,” a NAND gate outputs a logical “0” for this same combination of inputs. The symbol and truth table for a NAND gate is shown in Figure 1. The Boolean expression for a NAND gate with two inputs (A, B) and output X is:

NAND Gate Symbol Truth Table

Figure 1. Symbol and truth table for NAND gate

What are NAND gates used for?

NAND gates help detect if a single input to a digital system has gone low. For example, a simple security system consisting only of NAND gates could be used to monitor the status of sensors connected to windows and/or doors. If a window/door is closed, the sensor sends a logical “1” signal to the security system. While all windows and doors are closed, the alarm output is “0.” If a single window or door is opened, the security system output changes state to become “1” and this can be used to trigger an alarm or take some other action.

The popularity of the NAND gate is derived from the fact that it is the easiest of the digital logical operators to implement using transistor technology, e.g., a two-input NAND gate uses only four transistors when implemented in CMOS. All other logical operators can be implemented using only NAND gates connected in different configurations. Early microprocessors were implemented using only this trivial circuit.

Learn more:

See Also: Gate

Nanovolt Nanovolt (nV): Unit of measure. A billionth of a volt.
NC Normally closed (switch contacts)

Noise figure

Learn More: Noise Figure Measurement Methods and Formulas

NIC Network interface card
NiMH Nickel metal hydride: A rechargeable-battery technology.
NMI Nonmaskable interrupt
nMOS An n-channel metal-oxide semiconductor (nMOS) transistor is one in which n-type dopants are used in the gate region (the "channel"). A positive voltage on the gate turns the device on.
NO Normally open (Switch contact)
Non-Inverting Op Amp

A non-inverting op amp is an operational amplifier circuit with an output voltage that is in phase with the input voltage. Its complement is the inverting op amp, which produces an output signal that is 180o out of phase.

What is a non-inverting input?

An amplifier’s non-inverting input refers to the pin configuration. The non-inverting input is the terminal marked with a plus (+) sign, and the inverting input is marked with a minus (-) sign. These can also be referred to as positive and negative terminals.

Circuit diagram symbol for an op amp with non-inverting and inverting inputs.

Circuit diagram symbol for an op amp with non-inverting (+) and inverting (-) inputs.

What is the formula for a non-inverting amplifier?

Non-inverting op amps work following the op amp golden rules:

  1. The Current Rule: No current flows into the inputs of the op amp (I+=I-=0).
  2. The Voltage Rule: The output of the op amp attempts to ensure that the voltage difference between the two inputs is zero (V+=V-).

Non-inverting op amp circuit.

Non-inverting op amp circuit.

Consider the non-inverting op amp circuit shown above. According to the Voltage Rule, the voltage at the inverting (-) input will be the same as at the non-inverting (+) input, which is the applied voltage Vin.

The current going through R1 can then be given as Vin/R1.

According to the Current Rule, the inputs draw no current, so all that current must then flow through R2.

The output voltage can then be given as Vout=Vin+(Vin/R1)R2.

The gain is then Vout/Vin=1+(R2/R1).

The gain will never be less than 1, so the non-inverting op amp will produce an amplified signal that is in phase with the input.

What is the difference between an inverting and non-inverting amplifier?

A non-inverting amplifier produces an output signal that is in phase with the input signal, whereas an inverting amplifier’s output is out of phase. Both the inverting and non-inverting op amps can be constructed from one op amp and two resistors, just in different configurations.

Learn More:

Nonvolatile Nonvolatile (NV) RAM is memory which retains its stored value when power is removed.
Notch Filter

A notch filter is a type of band-stop filter, which is a filter that attenuates frequencies within a specific range while passing all other frequencies unaltered. For a notch filter, this range of frequencies is very narrow.

The range of frequencies that a band-stop filter attenuates is called the stopband. The narrow stopband in a notch filter makes the frequency response resemble a deep notch, which gives the filter its name. It also means that notch filters have a high Q factor, which is the ratio of center frequency to bandwidth.

What kind of filter is a notch filter?

A notch filter can be either active or passive depending on the design. A passive filter is one made of only passive elements, i.e. resistors, capacitors, and inductors. Active filters contain an amplifying element, such as an op amp, which is used in some notch filters.

What is a notch filter used for?

Notch filters are used to remove a single frequency or a narrow band of frequencies. In audio systems, a notch filter can be used to remove interfering frequencies such as powerline hum. Notch filters can also be used to remove a specific interfering frequency in radio receivers and software-defined radio.

How do you make a notch filter?

Notch filters can be created from a combination of high-pass and low-pass filters. See our tutorials on how to make a notch filter.

Learn More:

Noxious Fumes A combination of inert and corrosive gases usually associated with exhaust fumes or industrial by-products gases which can cause corrosive effects on temperature and pressure sensors when exposed.
NPR Noise-power ratio
NRD Nonradiative dielectric
NRE Nonrecurring engineering — one-time engineering costs associated with a project.
NRZ Non Return to Zero: A binary encoding scheme in which ones and zeroes are represented by opposite and alternating high and low voltages, and where there is no return to a zero (reference) voltage between encoded bits. That is, the stream has only two values: low and high.
ns Nanosecond(s)
NTC Negative temperature coefficient
nth A tiny, tiny amount. Pronounced "enth." From 1/n, which is one "nth."

NTSC is the color television standard established by the National Television Standards Committee in the United States in 1953. The NTSC standard's distinguishing feature was that it added color to the original 1941 black and white television standard in such a way that black and white TVs continued to work.

Another distinguishing characteristic was that NTSC's dependency on accurate phase meant that it was difficult to maintain the color as the signal was transmitted and processed. Television engineers often joke that NTSC stands for "Never Twice the Same Color."

The NTSC standard adds a color subcarrier which is quadrature-modulated by two color-difference signals and added to the luminance signal. The genius of the system is that black and white TVs ignore the color components, which are beyond the black and white signal's bandwidth.

The NTSC color subcarrier reference is 3.579545MHz. The horizontal sync rate (H) was adjusted slightly from the black and white standard's 15.750kHz such that the color subcarrier is 455/2 times H. The vertical rate is Fv = Fh x 2/525.

Learn More: Video Basics

NV-S Nanovolt seconds
nW Nanowatt(s)
Nyquist In A/D conversion, the Nyquist principle (derived from the Nyquist-Shannon sampling theorem) states that the sampling rate must be at least twice the maximum bandwidth of the analog signal in order to allow the signal to be reproduced. The maximum bandwidth of the signal (half the sampling rate) is commonly called the Nyquist frequency (or Shannon sampling frequency).

In real life, sampling rate must be higher than that (because filters are not perfect). As an example, the bandwidth of a standard audio CD is a bit shy of the theoretical maximum of 22.05kHz (based on the sample rate of 44.1kHz).

Also see:

OC Overcurrent
OC-48 A fiber-optic line capable of 2400 megabits per second.
OEM Original equipment manufacturer
OFC Open fiber control
OFDM Orthogonal Frequency Division Multiplexing: A method for multiplexing signals which divides the available bandwidth into a series of frequencies known as tones. Flarion uses the 5GHz channel and divides each channel into 400 discrete tones (each at slightly different frequency). Orthogonal tones do not interfere with each other when the peak of one tone corresponds with the null. All frequencies fade but the rapid switching, frequency-hopping technique is intended to allow more robust data service.
OLED Organic Light-Emitting Diode: An LED made with organic materials. The diodes in displays made with OLEDs emit light when a voltage is applied to them. The pixel diodes are selectively turned on or off to form images on the screen. This kind of display can be brighter and more efficient than current LCD displays.

OLED technology uses organic (carbon-based) materials, instead of semiconductor (e.g., Silicon, Indium) materials used by standard LEDs. Each pixel of an OLED display comprises a red, green, and blue diode (Figure 1) which emit light when a voltage is applied to them. Each diode can be switched on and off in different combinations and with different intensities to illuminate pixels, which then combine to create images on a screen.

What is the Difference Between OLED and WLED?

WLED (white light emitting diode) is a term usually associated with television and mobile phone LCD displays. Although WLED is marketed as being in some way “different” or “superior” to standard LEDs, WLED and LED technology are identical using semiconductor materials. The white light produced is used as a ‘backlight’ for LCD displays and is created by applying an electric field to a blue (or UV) LED and then filtering the emitted light through a material of a different colour (e.g., a yellow phosphor). The combination of the light and filter create (almost) white light. In an LCD display, this light is then polarized using arrays of many liquid crystals, which operate under the influence of variable electric fields to create images on a screen.

What are the Relative Advantages and Disadvantages of OLED/WLED?

The main advantage of OLED technology is that it allows displays to be much thinner (up to 10x) than displays made using LCD technology (with WLED backlight). Another important advantage is that because OLED displays do not need a backlight, they consume less power. This is critical for battery-powered displays (e.g., smartphones) as it means the battery does need to be charged as often. However, some disadvantages of OLED displays are that they are less water-resistant and the colors they produce deteriorates over time.

rbg diodes in oled display

Figure 1. RGB diodes in an OLED display

Learn MoreLED Driver ICs

OLT Optical line transmission
ONU ONT (Optical Network Termination), also called ONU (Optical Network Unit), refer to the consumer end equipment in an optical Fiber to the Home (FTTH) link. The ONT/ONU receives downstream data from the OLT (Optical Line Termination) through the passive optical splitters and provides video, voice, and broadband services to the consumer.
Op amp

Operational amplifier: The ideal op amp is an amplifier with infinite input impedance, infinite open-loop gain, zero output impedance, infinite bandwidth, and zero noise. It has positive and negative inputs which allow circuits that use feedback to achieve a wide range of functions.

Operational Amplifier Symbol

Operational Amplifier Symbol

Using op amps, it's easy to make amplifiers, comparators, log amps, filters, oscillators, data converters, level translators, references, and more. Mathematical functions like addition, subtraction, multiplication, and integration can be easily accomplished.

Practical, real-world op amps have finite characteristics but in most applications, are close enough to the ideal to make a huge range of inexpensive, high-performance analog applications possible. They are the building block for analog design.

One key to op amp design is nodal analysis. Since the input impedance is infinite, the current in and out of the + and - input nodes defines the circuit's behavior.

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An open-drain or open-collector output pin is driven by a single transistor, which pulls the pin to only one voltage (generally, to ground). When the output device is off, the pin is left floating (open, or hi-z).

A common example is an n-channel transistor which pulls the signal to ground when the transistor is on or leaves it open when the transistor is off.

Open-drain refers to such a circuit implemented in FET technologies because the transistor's drain terminal is connected to the output; open-collector means a bipolar transistor's collector is performing the function.

When the transistor is off, the signal can be driven by another device or it can be pulled up or down by a resistor. The resistor prevents an undefined, floating state. (See the related term, hi-z.)

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OR Combining two signals so that the output is on if either signal is present. This can be accomplished by an OR logic gate (two inputs, one output which is high if either input is).

It can also be done with a "wired-OR" connection in which two signals are simply wired together and either one of them can raise the level. This works when the signals are driven by a source that only pulls up or only pulls down, with a resistive load (e.g. an "open collector" output).


What is an Oscillator?

An electronic oscillator circuit generates an electrical signal which varies periodically in amplitude (voltage) over time such as a sine wave, square-wave, or triangle wave.

While some electronic oscillator circuits produce a signal of a fixed amplitude and frequency, in many oscillator circuits the amplitude can be increased or decreased (within design parameters) as required and the frequency of the signal can be varied (tuned). A signal generator is an example of an electronic oscillator (Figure 1).

 oscillator signal generator

Figure 1. Signal Generator

How can you see a signal from an Oscillator?

The signal produced by an electronic oscillator can be viewed using a piece of equipment called an oscilloscope, which displays the signal on a screen where the y-axis represents voltage and the x-axis represents time.

oscilloscope oscillator

Figure 2. Oscilloscope

The length of time that elapses before a signal begins to repeat is called the wavelength (λ) and this is the inverse of its frequency (F). The relationship between frequency and wavelength is as follows:

F = 1/λ


What do the terms “Amplitude” and “Wavelength” mean?

The difference between the maximum displacement and average of a signal is called the amplitude or peak voltage (Vpk).

Most modern oscilloscopes can be programmed to automatically show the voltage and frequency of the displayed signal.


Learn More: Silicon and Crystal Oscillators

Output to Input Ratio The ratio between the sensed current and the output current of the amplifier.
Overvoltage Protection

Overvoltage Protector (OVP) refers to a circuit that protects downstream circuitry from damage due to excessive voltage.

An OVP monitors the DC voltage coming from an external power source, such as an off-line power supply or a battery, and protects the rest of the connected circuitry using one of two methods: a crowbar clamp circuit or a series-connected switch.

The crowbar short-circuits or clamps the supply line to limit the voltage, possibly triggering other forms of protection such as a fuse.

The series-connected switch uses a MOSFET or transistor connected as a switch in series with the supply line. During an overvoltage condition, the OVP circuit rapidly shuts off the MOSFET and disconnects the downstream circuit.

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P-P Peak-to-peak
pA Picoampere(s)

A power amplifier (PA) converts a low-power signal to a higher power one. Two common examples are audio amplifiers, used to drive loudspeakers and headphones, and RF power amplifiers, such as those used in the final stage of a transmitter.

What are the types of power amplifier?

Power amplifiers are divided into classes based on the amplifier’s characteristics. Classes A, AB, B, and C depend on their conduction angle, which is the number of degrees in a cycle during which the amplifying device conducts. Classes D and E are switching amplifiers. Classes D, DG, and H are also common audio amplifiers that are similar to Class AB but use different techniques to improve efficiency.

Classes A-C

A Class A amplifier has a 360o conduction angle (100% of the input signal is used). It is the most linear, meaning the output signal is the best representation of the input. It is, however, the least efficient. Subsequent classes are increasingly efficient and decreasingly linear:

Class Conduction angle Input Signal Used Efficiency Linearity
A 360o 100% Lowest Highest
AB 180o-360o 50-100% Medium low Medium high
B 180o 50% Medium high Medium low
C <180o <50% Highest Lowest

Power amplifier conduction angle diagram

Class C amplifiers conduct for up to half of a period and Class B for exactly half. Class AB amplifiers conduct for 50-100% of the cycle and Class A amplifiers for the whole cycle.

Class D

Class D amplifiers use pulse-width modulation (PWM) to produce rail-to-rail digital output signal with a variable duty cycle to approximate the analog input signal. They are highly efficient because the output transistors are always either fully turned on or fully turned off.

Classes G and H

Class G amplifiers are similar to Class AB amps, except that they use two or more supply voltages and are more efficient because they use the maximum supply voltage only when required. Class H power amps are similar to Class G, but the Class H topology does not require multiple power supplies.

Class DG

The Class DG amp is similar to the Class D amp but also uses a multilevel output stage to sense the magnitude of the output signal. It then switches the supply rails as needed to supply the required signal power more efficiently.

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PAE Power-added efficiency

Phase alternate line: A television standard used in most of Europe.

Similar to NTSC, but uses subcarrier phase alternation to reduce the sensitivity to phase errors that would be displayed as color errors. Commonly used with 626-line, 50Hz scanning systems, with a subcarrier frequency of 4.43362MHz.

Learn More: Video Basics

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Parallel Interface A parallel interface (as distinguished from a serial interface) is one in which data is sent on several wires (or several wireless channels) at once. Examples: GPIB, byte-wide parallel interfaces to data converters, memory and data buses on computer boards and backplanes.

In contrast, a serial interface uses one wire or wire-pair or wireless channel (or one in each direction).

Parasite Power The device derives its supply power directly from the serial interface (1-Wire).
Partition Locking The ability to lockout writes and/or reads to certain sections of the memory.
PBC Port bypass circuit
pC 1. pC: Picocoulomb(s), a unit of electrical charge.

2. PC: Printed circuit (see: Printed Circuit Board).

3. PC: Personal Computer.
PC Card Add-in cards that conform to the PC Card specification (formerly called PCMCIA). A PC Card is a removable device, approximately the size of a credit card, designed to plug into a matching slot.
PCI Peripheral Component Interconnect: A standard interface used primarily on computer backplanes to connect interface cards and peripheral devices to the processor bus. PCI is often used for video display cards, network interfaces (e.g. Ethernet), and peripheral interfaces such as SCSI or USB.

PCI buses typically also support the older Industry Standard Architecture (ISA) standard.

PCI Express PCI Express® (Peripheral Component Interconnect Express), officially abbreviated as PCIe®, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP standards. It is used to link motherboard-mounted peripherals and as an expansion card interface for add-in boards.

The PCIe electrical interface is also used in a variety of other standards, most notably the ExpressCard laptop expansion card interface.

Source: Wikipedia

PCM Pulse-Code Modulation (PCM) is the conversion of an analog signal (e.g. audio) into digital, binary (0 or 1), coded pulses, decreasing noise susceptibility. PAM, PFM and PWM are examples of PCM methods.
PCMCIA Personal Computer Memory Card International Association: A standard for miniaturized laptop expansion cards for modems, storage, and other devices. The standard was officially renamed "PC card."
PCS Personal Communications Service: An American generic term for a mass-market mobile phone service, emphasizing personal communication, independent of the technology used to provide it. PCS includes such digital cellular technologies as GSM 1900, CDMA and TDMA IS-136. 2G, CDMA, Digital, GSM, TDMA.

Personal digital assistant.

Learn More: PDA Solutions

See Also: Bluetooth

PDC Personal Digital Cellular: The digital wireless standard used in Japan. PDC uses TDMA air interface.
PDI Phase-detector input
PDJ Pattern-dependent jitter
PDM Pulse density modulation
PDO Phase-detector output
Peak Inverse Voltage Peak Inverse Voltage (PIV) or Peak Reverse Voltage (PRV) refer to the maximum voltage a diode or other device can withstand in the reverse-biased direction before breakdown. Also may be called Reverse Breakdown Voltage.

Note that PIV is also an abbreviation for FIPS 201 Personal Identity Verification.

PECL Positive-referenced emitter-coupled logic
pF Picofarad. A Farad is the unit of capacitance. A pF is 10-12 of a Farad. (1000pF = 1nF, 1000nF = 1 microfarad).
PFD Phase/frequency detector
PFI Power-fail input
PFM Pulse-Frequency Modulation: A pulse modulation technique in which the frequency is varied with the input signal amplitude. The duty cycle of the modulated signal does not change. Because it is always a square wave with changing frequency, PFM is also referred to as square-wave FM.
PFMEA Process Failure Mode and Effects Analysis (PFMEA): A methodology for assessing the weaknesses of production processes and the potential effects of process failures on the product being produced.
PFO Power-fail output
PG Power-good; power gain
PGA Programmable Gain Amplifier: An amplifier whose gain can be varied by a separate input (usually a digital value).

See: Programmable-Gain Amplifier, Using the MAX532 DAC

Pin Electronics

Electronic circuitry in an automated tester (ATE system) that connects to the device under test.

Pin electronics can deliver signals, power, or precise voltages and currents, and can measure the pin's response, drive, and electrical characteristics.

Learn More: Automatic Test Equipment Guide

PKI Public Key Infrastructure: A combination of standards, protocols, and software that creates, edits, and revokes digital public key certificates.
PLA Programmable logic array
PLC A Programmable Logic Controller (PLC, or Programmable Controller) is a ruggedized, microprocessor-based system which provides factory or plant automation by monitoring sensors and controlling actuators in real time.

See: Maxim Solutions for PLCs.

PLC is also used as an acronym for Powerline Communications (HomePlug).

PLCC Leaded Chip Carrier, also called PLCC or Plastic Leaded Chip Carrier: A square surface mount chip package in plastic with leads (pins) on all four sides. Example: Maxim 20-pin LCC diagram (PDF)
Plesiochronous Digital Hierarchy The time-division multiplexed network used by telecommunications companies to transport phone calls and data over copper cabling. The entire network shares a common frequency throughout it's tree-like structure, although phase and time delay variations exists at various points along the edge of the network.

A phase-locked loop (also phase lock loop or PLL) is a system that generates an output signal whose phase is related to its input. The two signals will have the same frequency and either no phase difference or a constant phase difference between them.

A PLL typically consists of a phase detector, a loop filter, and a voltage-controlled oscillator (VCO). The phase detector compares the reference signal with the oscillator frequency and outputs an error signal. The loop filter (usually a low-pass filter) then generates an error voltage from the error signal. The VCO then increases or decreases the oscillator frequency to lock to the input frequency. This produces an output frequency that is equal to the input frequency, and a constant phase shift (which could be zero) between the two signals. A PLL may also have a frequency divider in its feedback loop in order to create an output that is a multiple of the reference frequency instead of one that is exactly equal to it.

Block diagram of a basic phase-locked loop

Block diagram of a basic phase-locked loop, with phase detector, loop filter, VCO, and optional frequency divider.

What are the three stages through which a PLL operates?

The three stages of a phase-locked loop are free running, capture, and phase lock or tracking:

  • Free running- the center frequency of the PLL, which is the frequency that the VCO runs at when not locked to the input frequency.
  • Capture- in order for the VCO to lock to the input frequency initially, the frequency must be within the PLL’s capture range.
  • Phase lock (or tracking)- once the VCO has locked to the input frequency, it will continue to track and adjust to the input frequency as long as it stays within the PLL’s lock range. The lock range is wider than the capture range.

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PLM Pad limiting metal
PMIC Power Management Integrated Circuit: Circuits used to regulate and control power.
PMM Power-management mode
Pmods are small I/O interface boards used to extend the capabilities of FPGA/CPLD and embedded control boards. Pmods communicate with system boards using 6- or 12-pin connectors.
Pmod is the trademark of Digilent Inc.
pMOS A p-channel metal-oxide semiconductor (pMOS) transistor is one in which p-type dopants are used in the gate region (the "channel"). A negative voltage on the gate turns the device on.
PMR Private Mobile Radio: Radio bands generally for use within a defined user group, such as the emergency services or by the employees of a mining project.

Power-over-Ethernet: A means for delivering power to a remote device using the same cable lines used to deliver Ethernet data.

Learn More: Power Over Ethernet Devices


Point-of-load (POL) power supplies solve the challenge of high peak current demands and low noise margins, required by high-performance semiconductors such as microcontrollers or ASICs, by placing individual power supply regulators (linear or DC-DC) close to their point of use.

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POK Power-OK
PON Passive optical network: A cost-effective way to provide high performance Fiber to the Home (FTTH) connectivity via shared optical fiber. PON connects up to 32 (or more) homes on the same network using passive optical components (splitters).
POP Analysis

Periodic Operating Point (POP) Analysis is a simulation technique (used by EE-Sim) to find the steady state operation condition of a switching power supply design.

One conversion cycle is run in the time domain. The inductor currents and capacitor voltages at the beginning of that cycle are compared to the inductor currents and capacitor voltages at the end of that cycle. When the difference has been driven below 10-9, the steady state conditions are identified and POP Analysis ends.

Learn More: EE-Sim

POR Power-on reset

A potentiometer (also pot or electronic pot) is a variable resistor in which a wiper sweeps from one end of the resistive element to the other, resulting in resistance that is proportional to the wiper’s position.

How does a potentiometer work?


A potentiometer has three terminals, shown in green, red, and blue in the diagram. The red is the wiper that can be adjusted to vary the resistance between it and the other two terminals. By increasing the resistance between the green and the red, the resistance is decreased between the red and the blue. The resistance between the green and blue terminals remains constant.

The potentiometer symbol is a resistor symbol with an arrow representing the variable wiper.

The potentiometer symbol is a resistor symbol with an arrow representing the variable wiper.

What is the difference between A and B potentiometers?

The relationship between the wiper position and the resistance is referred to as the “taper,” which can either be linear or logarithmic. In a linear taper, the resistance is proportional to the distance between the wiper and the terminal. In a logarithmic taper, either the size or material of the resistive element is not uniform from one end to the other in order to create a resistance that varies as a logarithmic function instead of a linear one.

A letter code may be given by the manufacturer to distinguish between linear and logarithmic taper. Manufacturers in the U.S. and Asia will usually mark potentiometers as type A for logarithmic and type B for linear. Manufacturers in Europe often do the reverse, with A being linear and B logarithmic.

What kind of potentiometer do I need?

When using a mechanical pot, the wiper position is adjusted manually. In many cases, it is advantageous to use a digital pot, where the wiper position is digitally controlled in order to provide a resolution that is fully specified and repeatable. For more on mechanical and digital pots, see App Note 3484: Upgrading from Mechanical Potentiometers to Digital Pots.

Potentiometers vary by taper, end-to-end resistance, and size. Digital potentiometers also vary by number of steps, type of control interface, and whether the wiper memory is volatile or non-volatile. For more on how to choose a potentiometer for a specific application, see App Note 4101: Differentiating Digital Potentiometer Features.

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Power Added Efficiency

In an RF power amplifier, power added efficiency (PAE) is defined as the ratio of the difference of the output and input signal power to the DC power consumed.

The formula for power added efficiency is:


Power Fail A feature in a microprocessor supervisory circuit that provides early warning to the microprocessor of imminent power failure.
PowerCap A special surface-mount package with access to the internal cavity via an openable top. This packaging scheme allows easy upgrade of NV RAMs without having to change the PCB hardware layout. The user can simply open the lid and swap out the IC.
PPAP Production Part Approval Process. Used by automotive industry for acceptance of new products for release and use on automobiles.
PRBS Pseudorandom binary (bit) sequence
PRC Parasitic resistance cancellation
PRCM Parasitic resistance cancellation mode
Pre-Bias Soft Start

Pre-bias soft start is a power-supply feature that prevents discharging of the output capacitor when the power supply starts up.

Discharging the output capacitor could create either start up oscillation problems at cold start or large voltage disturbances on the output voltage bus at hot plug-in. Pre-bias soft start is an important feature in redundant power-supply systems, parallel power supply modules, battery back-up voltage buses, and other applications where multiple power sources supply one node.

Learn More: MAX1917 Provides Pre-Bias Soft Start for Redundant Supply

See Also: Soft Start

Preemphasis In some transmission and recording systems (e.g. vinyl records, FM radio, analog magnetic tape), there is more noise at higher frequencies. To offset this, the audio signal is "preemphasized" at the transmitter -- filtered with a high-pass filter to boost the higher audio frequencies. A matching low-pass filter is used at the receiver to return to an overall flat audio-frequency response. The filter at the receiver reduces the high-frequency noise introduced by the transmission process.
Pressure Cooker Test A Pressure Cooker Test (PCT) tests a part under high temperature, humidity, and pressure conditions. Also called an Autoclave Test or Pressure Pot Test (PPOT).
Printed Circuit Board

A printed circuit board, or PC board, or PCB, is a non-conductive material with conductive lines printed or etched. Electronic components are mounted on the board and the traces connect the components together to form a working circuit or assembly.

A PC board can have conductors on one side or two sides and can be multi-layer — a sandwich with many layers of conductors, each separated by insulating layers.

The most common circuit boards are made of plastic or glass-fiber and resin composites and use copper traces, but a wide variety of other materials may be used. Most PCBs are flat and rigid but flexible substrates can allow boards to fit in convoluted spaces.

Components are mounted via SMD (surface-mount) or through-hole methods.

PRM Performance report message
PROCHOT# Digital output pin on Intel's Pentium 4 processors that indicates the internal Thermal Control Circuit has activated. This occurs when the processor has reached its maximum safe operating temperature.
PROFIBUS Vendor-independent open fieldbus standard used in manufacturing, building automation, and process control. Utilizes a nonpowered two-wire (RS-485) network. PROFIBUS is standardized under the European Fieldbus Standard EN 50 170. It includes three versions: FMS, DP, and PA. Visit for more information.
PROM Programmable read-only memory
PRT Platinum Resistance Thermometer, a resistance temperature device (RTD).
PS Power sense
PSD Preamble-switched diversity
PSK Phase-shift keying (PSK): A modulation technique in which the phase of the carrier conveys the input signal's information.
PSR Power-supply rejection

Power Supply Rejection Ratio (PSRR) is the ability of an amplifier to maintain its output voltage as its DC power-supply voltage is varied.

PSRR = (change in Vcc)/(change in Vout)

See also: Ripple rejection, which is degree of immunity from AC in the power supply.

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PSW Program status word
PTC Positive Temperature Coefficient (PTC): When the resistance of a component rises with temperature, it is said to have a positive temperature coefficient.

Example: Hewlett-Packard's first commercial product, an audio oscillator, used a common light bulb as a PTC element in the feedback circuit to maintain constant output amplitude regardless of frequency.

Pulse-Amplitude Modulation Pulse-Amplitude Modulation (PAM) is a pulse modulation technique in which the amplitude of the pulse is varied with the input signal amplitude.

An output structure which uses one active device to source current and a second device to sink current.

Common examples are: a CMOS stage in which an n-channel device pulls toward ground or a negative supply and a p-channel device pushes current to bring the output up; an output stage in an audio amplifier with an NPN and PNP device in totem-pole configuration.

Learn More: Regulator Topologies for Battery-Powered Systems

PV-S Picovolt second(s)
PVR Personal video recorder
PWD Pulse-width distortion
PWM 1. A method for using pulse width to encode or modulate a signal. The width of each pulse is a function of the amplitude of the signal.

2. A technique used to modulate the power delivered to a load.

In DC-DC switching regulators, the pulse width driving the main power switch (and hence, the duty cycle) is varied to maintain the desired output voltage. In DC motor-control applications, pulse width is used to vary motor speed.

PWM Temperature Sensor Temperature sensor with digital, logic-level output. The output has a fixed frequency and the duty cycle varies with the measured temperature.
Q Factor

A measure of the quality of a resonant (tank) circuit. A "high-Q" circuit has mostly reactive components (inductive and capacitive), with low resistance. It resonates strongly, with little damping (low loss). A high-Q circuit will have low bandwidth relative to its center frequency (that is, it will have a narrow bandwidth vs frequency curve).

Q = 2 π * (Energy stored / Energy dissipated per cycle)

Learn More: A Beginner's Guide to Filter Topologies


Quadrature Amplitude Modulation (QAM) is a modulation method in which two signals are used to amplitude-modulate two carriers that are in quadrature (90 degrees out of phase with each other). The two modulated signals are combined.

A common application is in PAL and NTSC color television transmission. Color is encoded into two analog signals (called I and Q), which modulate quadrature color carriers.

Modems also use this approach, to increase the data bandwidth they can carry (or, more accurately, to trade bandwidth for error rate or noise immunity).

Learn More: Video: From Amplitude Modulation (AM) to Quadrature Amplitude Modulation (QAM)


"Quad, flat, no-lead" package.

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QFP Quad flat pack, a package type.

Quadrature Phase Shift Keying (QPSK) is a form of Phase Shift Keying in which two bits are modulated at once, selecting one of four possible carrier phase shifts (0, 90, 180, or 270 degrees).

QPSK allows the signal to carry twice as much information as ordinary PSK using the same bandwidth. QPSK is used for satellite transmission of MPEG2 video, cable modems, videoconferencing, cellular phone systems, and other forms of digital communication over an RF carrier.

Learn More: QPSK Modulation Demystified

QRSS Quasi-random signal source
QS-9000 QS-9000 is the automotive quality standard surperseded by ISO/TS16949:2002 specification for component suppliers to the automotive industry.
QSOP Quarter small-outline package
Quadrature The relation between two waves of the same frequency, but one-quarter of a cycle (90°) out of phase.

Quantization is a process whereby the continuous range of input-signal values is divided into nonoverlapping subranges.

Each of these subranges has a discrete value of the output uniquely assigned. Once a signal value falls within a given subrange, the output provides the corresponding discrete value.

Learn More: How Quantization and Thermal Noise Determine an ADC's Effective Noise Figure

QuERC Software that examines bias and transient simulation output and flags devices operating above limits. Querc is supplied by Maxim to ASIC customers.
Quiescent For an electronic circuit, a quiet state in which the circuit is driving no load and its inputs are not cycling. Most commonly used for the specification "quiescent current," the current consumed by a circuit when it in a quiescent state.
R-2R 1. Short for R-2R ladder: A method for D/A conversion which employs a ladder-shaped resistor array composed of two resistor values: R and 2R. Each bit in the digital input switches a ladder's rungs in and out of the network to change the output voltage by an amount proportional to the significance of the bit.

2. Rail-to-rail

RAC Remaining absolute capacity (mA-hr)
RAID Redundant Array of Independent Disks: A redundant array of inexpensive disks. RAID is a performance-enhancing method of storing the same data in different places on multiple hard disks to achieve speed and/or data redundancy.
Rail-to-Rail Input The allowable input signal range includes the supply voltages.
Rail-to-Rail Input or Output The allowable input and output voltage ranges include the power-supply rails.
RAM Random access memory
Random Jitter

Random jitter (RJ) includes all jitter components not defined as deterministic jitter (i.e., the jitter that is not related to the signal and known noise sources).

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RAR Remaining active runtime (min)
RC Resistance-capacitance; resistor-capacitor. In particular, an RC network is a network composed of resistors and capacitors in a series-parallel combination, usually to filter or delay a signal.
RE Remaining energy (joules)
Receiver A circuit that accepts signals from a transmission medium (which can be wireless or wired) and decodes or translates them into a form that can drive local circuits.


  • A radio receiver that detects and demodulates the signal from the airwaves
  • An ultrasonic receiver that turns ultrasound signals into electrical signals
  • A line receiver that receives signals from a wire or backplane
  • A standard interface receiver (e.g., USB, serial, LVDS)
  • A fiber optic device that translates light pulses into electrical signals
Recovery Time The time for a sensor to return to baseline value after the step removal of the measured variable. Usually specified as time to fall to 10% of final value after step removal of measured variable.

REF is a term that appears on IC package drawings in reference to dimensions. It stands for REFERENCE and indicates that this is a reference dimension, calculated or based on another dimension.

For example, the dimension from the first pin to the last pin in the row of a DIP (dual inline package) usually is tagged as REF because it is a multiple of the distance from pin-to-pin. In the case of a 16-pin DIP, the first pin to last pin dimension is 7 times the pin-to-pin dimension (7 spaces between 8 pins).

Learn More: Package Materials

See Also: BSC


A relay is an electromagnetic switching device consisting of an armature which is moved by an electromagnet to operate one or more switch contacts.

Some advantages of relays are that they provide amplification and isolation and are straightforward. They can switch difficult voltages (e.g. RF or high-powered AC) with complete isolation and no worries about level translation.

Relay disadvantages, compared to solid-state switching, include power efficiency, noise (both mechanical and electrical, including "contact bounce"), size, speed, and reliability. Analog switches are commonly used instead of relays in signal switching applications.

Driving a relay can be tricky because it's an inductive load. Special relay drivers are often used.

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Remote Diode A diode or diode-connected bipolar transistor used as a temperature-sensing element, often integrated onto an integrated circuit whose temperature is to be measured.
Remote Temperature Temperature at a location other than at the die of the temperature-measuring integrated circuit.
Remote Temperature Sensor A remotely located PN junction used as a temperature sensing device, usually located on an integrated circuit other than the one doing the measurement.
Resistance Resistance, represented by the symbol R and measured in ohms, is a measure of the opposition to electrical flow in DC systems. Resistance is the voltage across an element divided by the current (R = V/I).
Resonant Circuit

A resonant, or tuned, circuit combines an inductor and capacitor (or mechanical equivalents such as a crystal or MEMS oscillator) to make a circuit that is responsive to a frequency.

Depending on the configuration, the circuit can have a high or low impedance at the resonant frequency and operate as bandpass or band stop filter, or an oscillator.

It may be called an LC or LRC circuit because of the inductive (L), resistive (R), and capacitive (C) components used.

An older name is "tank circuit," because its operation is analogous to a tank in a fluid system, in which the dimensions of the tank define the natural frequency observed when fluid is pulsed through the tank.

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Response Time The time for a sensor to respond from no load to a step change in load. Usually specified as time to rise to 90% of final value, measured from onset of step input change in measured variable.
Reverse Recovery Time When switching from the conducting to the blocking state, a diode or rectifier has stored charge that must first be discharged before the diode blocks reverse current. This discharge takes a finite amount of time known as the Reverse Recovery Time, or trr. During this time, diode current may flow in the reverse direction.
RF Radio Frequency: An AC signal of high enough frequency to be used for wireless communications.
RFDS Radio frequency design system
RFI Radio Frequency Interference: Unwanted noise from RF sources.
RFID Radio Frequency Identification: A method for uniquely identifying an object using a tag or module that carries a unique ID number, or code. Identification can be made using wireless (RF, or radio-wave) connection, meaning no line-of-sight or physical contact is needed. There are many different ways to achieve RFID and many applications including pet ID, identification of parts on an assembly line, tracking goods in manufacturing or retail settings, etc.

Also see: NFC/RFID Products

RFPF Positive reference
RH Relative humidity
RI Reference input; ring indicate
RIAA Recording Industry Association of America
Ripple Rejection Ripple Rejection is the ability of an amplifier to maintain accurate output voltage despite AC fluctuations in the power supply.
RISC Reduced instruction set computer (RISC): Computer hardware designed to support a short list of simple instructions. This makes the hardware simpler and faster, since it does not need to accommodate complex instructions.

Although more instructions must be executed for some operations, a RISC architecture can be faster, depending on the instruction mix, the design of the instruction set, and how effective the compilers and support software are in translating operations into optimized instructions.

RMS Root mean square
RNPF Negative reference
ROM Read-only memory
RRC Remaining relative capacity: The percent of the full charge that remains in a power cell.

RS-232 is a serial interface published by the EIA for asynchronous data communication over distances up to a few hundred feet.

Characterized by a single-ended (not differential) physical layer, it uses one signal wire for transmission, another for reception, and a common wire (ground), plus some timing and control signals. Its specifications are rooted in electromechanical equipment signaling (Teletype machines). Still a very common interface but largely replaced by USB in recent years.

The term "serial" interface is often used for an RS-232 interface. The usage is not quite accurate—while RS-232 is a serial interface, there are other serial interfaces in addition to RS-232.

When it was introduced in 1987, the MAX232 rapidly became the most common way to implement RS-232 because it required only a single 5-volt supply. On-board DC-DC converters developed the odd voltages required by the official spec. Maxim still manufacturers the MAX232 and makes a wide range of newer products as well.

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RS-422/RS-485 RS-485 and RS-422 are serial interface standards in which data is sent in a differential pair (two wires, or twisted pair cable), which allows greater distances and higher data rates than non-differential serial schemes such as RS-232. See: Differential Signaling.

RS-485 and RS-422 can be configured for full-duplex or half-duplex bus systems.

See Selecting and Using RS-232, RS-422, and RS-485 Serial Data Standards to learn about the differences between RS-232, RS-422, and RS-485.

RSA A public key cryptographic algorithm named after its inventors (Rivest, Shamir, and Adelman). It is used for encryption and digital signatures. RSA was developed in 1977 and is today the most commonly used encryption and authentication algorithm.
RSR Remaining standby runtime (min)
RSSI Received Signal Strength Indicator (or Indication): A signal or circuit that indicates the strength of the incoming (received) signal in a receiver. (The signal strength indicator on a cell phone display is a common example).

RSSI is often done in the IF stage before the IF amplifier. In zero-IF systems, it is done in the baseband signal chain, before the baseband amplifier.

RSSI output is often a DC analog level. It can also be sampled by an internal ADC and the resulting codes available directly or via peripheral or internal processor bus.


A real-time clock (RTC) is an integrated circuit that contains a timer that supplies the time of day (and often, the date). An RTC generally contains a long-life battery to allow it to keep track of the time even when there is no power applied.

Learn More: Real-Time Clocks

RTD A Resistance Temperature Detector (RTD) is a device with a significant temperature coefficient (that is, its resistance varies with temperature). It is used as a temperature measurement device, usually by passing a low-level current through it and measuring the voltage drop. A thermistor is a common type of RTD.
RTS Request to send: A data communications signal (e.g. RS-232)
Rx Receive
RZ Return to Zero: A binary bitstream encoding scheme in which the signal returns to zero voltage in between the data bits. The signal has three valid levels: High, Low, and the return to zero volts after each bit.
S 1. Siemen(s), standard unit for conductance

2. Lower case s is the standard abbreviation for seconds.

S-Parameters The reflection and transmission coefficients used in impedance matching between high-speed (RF) devices and transmission lines/traces.
S-UMTS Satellite-universal mobile telecommunications system
S/S Single supply
Samples per Second

1. sps: Samples per second. In data conversion, an analog signal is converted to a stream of numbers, each representing the analog signal's amplitude at a moment in time. Each number is called a "sample." The number sample per second is called the sampling rate, measured in samples per second.

2. ksps: Kilosample(s) per second (thousands of samples per second)

3. Msps: Megasamples per second (millions of samples per second)

Learn More:

Sampling Rate

An ADC takes a continuous analog signal and converts it to a discrete digital signal by taking samples that represent the signal’s amplitude at specific points in time. The sample rate (or sampling rate) is the number of samples taken per second.

The units for sample rate are samples per second (sps) or Hertz (Hz). The two are equivalent since the Hertz is equal to the reciprocal second, [Hz]=[s-1]. Hertz is the unit for frequency, and the sample rate is sometimes referred to as the sampling frequency. Sample rate and sampling frequency represent the same value.

Is a higher sample rate better?

For a sampled signal to be free of distortion known as aliasing, the Nyquist frequency of the sampler must be greater than the highest frequency that needs to be preserved. The Nyquist frequency is equal to half of the sample rate, so increasing sample rate means that higher frequencies can be recorded without aliasing.

The Nyquist criterion sets a theoretical lower limit, and in practice, sample rates must be (sometimes much) greater than twice the highest frequency to be sampled for the signal to be accurately converted. Higher sample rates typically come at the cost of slower speeds and higher power consumption.

How does sample rate affect sound quality?

Audio signals are subject to the same criteria as other analog signals. Humans can hear sounds in the 20-20,000 Hz range, so music and other sound waves are often sampled at 44.1kHz or 48kHz (slightly over the Nyquist frequency). Audio is also sometimes recorded at 88.2kHz or 96kHz in a process known as oversampling, wherein the sample rate is taken to be well over the Nyquist frequency in order to improve resolution and signal-to-noise ratio.

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See Also:

SAN Storage Area Network: A network infrastructure of shared multihost storage, linking all storage devices and interconnecting remote sites.

Successive Approximation Register: Used to perform the analog-to-digital conversion in successive steps in many analog-to-digital (ADC) converters.

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SAW Surface Acoustic Wave: A sound wave that propagates along the surface of a solid and is contained within the solid. SAW devices typically combine compressional and shear components. In Wireless applications, SAW refers to a Surface Acoustic Wave band-pass filter, which exhibits much better out-of-band rejection, but has higher passband ripple and insertion loss.
SB Side braze
SBGA Super ball-grid array, a packaging technology.
SBS Smart Battery Specification: A specification developed by Duracell.
Scan Design A design technique in which the internal registers or flip-flops of a circuit can be chained, to allow an external circuit to easily read and write their contents.

When internal memory elements are not directly accessible from the circuit's outside pins, testing is difficult because their state is unknown. With scan design, a signal reconfigures the elements into a "scan chain" and their contents can be read and if desired, altered.

SCART Also known as Euroconnector or Peritel, a 21-pin connector commonly used in Europe to interconnect satellite receivers, television sets, and other audiovisual equipment (e.g. videocassette recorders). A single connector combines audio and video signals. The name comes from "Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs."

Peritel is an abbreviation for "péritélévision." Peri is a prefix that means around or surrounding — in this case, it suggests the connection between the television and its electronic environment.

SCF Switched-capacitor filter
Schottky Diode A diode realized via a "Schottky-barrier junction" -- a metal-semiconductor junction -- rather than the P-N junction used by conventional semiconductor diodes. Schottky diodes are often chosen for their high switching speed and low forward voltage drop.
SCL Serial clock line
SCLK Serial clock
SCR Silicon-controlled rectifier
SCSI Small Computer System Interface (pronounced "scuzzy"), an interface standard for connecting peripheral devices to computers. Hardware components for implementing a SCSI interface include connector ports on computers and cables for connecting peripheral devices to the computer. SCSI is gradually being supplanted by the newer USB and IEEE 1341 standards.
SCT Single Chip Transceivers: A single IC that includes data communication transmitter and receiver functions.
SD 1. Signal detect: An output that indicates when a signal is present. A form of Signal Strength Indicator.

2. Secure Digital, a media format for nonvolatile external memory. The successor to the "MultiMedia Card" format, or MMC, SD card memories typically operate from 3.3V supplies with modest current requirements. SD memory cards are best known as storage for digital cameras, smart phones, and other consumer electronic devices.

SDA Serial data access
SDO Serial data out
SDTV Standard Definition Television: Digital formats that do not achieve the video quality of HDTV, but are at least equal, or superior to, NTSC pictures. SDTV may have either 4:3 or 16:9 aspect ratios, and includes surround sound. Variations of fps (frames per second), lines of resolution, and other factors of 480p and 480i make up the 12 SDTV formats in the ATSC standard.
Second Harmonic Distortion Second harmonic distortion (HD2): Ratio of second-order harmonic to the input signal (carrier). Often measured as dBc.
Secure Hash Standard This standard specifies a Secure Hash Algorithm, SHA-1, for computing a condensed representation of a message or a data file.
Semiconductor 1. A substance that can act as an electrical conductor or insulator depending on chemical alterations or external conditions. Examples are silicon, germanium, and gallium arsenide.

Also called "III-V" materials since semiconductor elements are in groups III and V of the periodic table of chemical elements.

2. An electronic device (e.g. a transistor, diode, or integrated circuit) manufactured from semiconductor materials.

Semiconductor devices control and amplify because a small voltage or current, or a physical stimulus (such as light or pressure), allows the semiconductor to pass or block electrical current. Devices can be fabricated with other capabilities such as passing electric current in only one direction, emitting light, mixing and transforming signals, etc.

Sense Resistor A resistor placed in a current path to allow the current to be measured. The voltage across the sense resistor is proportional to the current that is being measured and an amplifier produces a voltage or current that drives the measurement.

An electrical sensor (also called an electronic sensor) is a device that detects a physical parameter of interest (e.g. heat, light, sound) and converts it into electrical signal that can be measured and used by an electrical or electronic system.

The detected quantity is usually a form of energy that is analog (continuous) in nature and is converted into electrical energy using a transducer (e.g. a microphone is a transducer that converts sound energy into electrical energy).

How Are Sensors Used?

The signal generated at the output of an electrical sensor is typically used for the purpose of making a measurement which can then be used to trigger a subsequent response. For example, a temperature sensor could be used to measure the temperature of a room and convert it into an electrical signal. If the measured room temperature is too low (below a pre-determined threshold) this information could be used by an electronic system that automatically switches on a heater to increase the temperature of the room back towards the pre-determined threshold. Alternatively, if the measurement from the sensor indicates that the room is too hot (above a pre-determined threshold), the system could automatically switch on an air-conditioning unit to reduce the room temperature. The common name for a sensor used to measure temperature is a thermometer.

Nowadays, the output signal from an electrical sensor is usually processed by a digital processor. To make this possible, the continuous analog electrical signal must first be converted into a discrete digital representation using an Analog-to-Digital converter.

Types of Sensors

Apart from heat and sound, electrical sensors can be used to detect and measure other quantities including light, pressure, speed, acceleration, and mass. The size of the signal produced by a sensor depends on the application e.g. Industrial sensors produce electrical signals typically between 20 and 30V while biosensors, used in health and fitness wearables (Figure 1) and which are used to make human body measurements, typically produce electronic signals of only a few millivolts or even smaller.

health sensor platform

Figure 1 Health Sensor Platform

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SEPIC Single Ended Primary Inductor Converter: A DC-DC converter topology that acts both as a boost and a buck converter (that is, will step up or down, depending on the input voltage).


Learn More: Video: What is a SerDes and why do I need one?

See Also:

Serial Interface A serial interface (as distinguished from a parallel interface) is one in which data is sent in a single stream of bits, usually on a single wire-plus-ground, wire-pair, or single wireless channel (or two sets, one for each direction). Examples include USB, RS-232, I2C, and 1-Wire.

By contrast, a parallel interface sends several bits at once, on separate wires.

SFDR Spurious-Free Dynamic Range: A term used to specify A/D and D/A converters (ADCs and DACs).

In ADCs, Spurious-Free Dynamic Range (SFDR) is the ratio of the RMS amplitude of the carrier frequency (maximum signal component) to the RMS value of the next largest noise or harmonic distortion component. SFDR is usually measured in dBc (with respect to the carrier frequency amplitude) or in dBFS (with respect to the ADC's full-scale range).

In DACs, Spurious-Free Dynamic Range (SFDR) is the ratio of the RMS amplitude of the carrier frequency (maximum signal components) to the RMS value of their next largest distortion component. SFDR is usually measured in dBc (with respect to the carrier frequency amplitude) or in dBFS (with respect to the DAC's full-scale range). Depending on the test condition, SFDR is observed within a pre-defined window or to Nyquist.

Also see the Maxim Data Conversion Calculator.

SFF Small Form Factor: An optical module.
SFF-8472 Small Form Factor: Specification for optical modules.
SFP Small Form Factor Pluggable
SFR Special-function register
SHA Secure Hash Algorithm: A message digest algorithm developed by the NSA for use in the Digital Signature standard, FIPS number 186 from NIST. SHA is an improved variant of MD4 producing a 160-bit hash. SHA is one of two message digest algorithms available in IPSEC.
SHDN Shutdown. Low-power standby mode.
Shift Register

A shift register is two or more bistable elements (flip-flops) connected in series. With each tick of the clock, the output of stage n is shifted to stage n+1. Applications include clock or signal delays, delay lines, and linear-feedback shift registers.

Shock Sensor

A shock sensor is an acceleration sensor, generally a piezoelectric type, that can measure high acceleration but cannot measure static g forces.

Shoot-Through Current In a push-pull amplifier stage, one transistor pushes current to the output to drive it toward a positive voltage; a second device pulls down. These are designed so both devices are never fully on, which would effectively short the power supply.

The rush of current that occurs while both devices are on is called the shoot-through current. Events that allow both devices to be on (e.g. circuit faults or a brief moment in the switching cycle) are said to "crowbar" the circuit because of its similarity to a power supply protection circuit of that name.

See: Protection and Isolation products.

Shutdown A feature of many Maxim ICs, typically controlled via a logic-level input, which dramatically reduces power consumption when the device is not in use.
SI Sampled input
SiGe Silicon Germanium process
Signal-Invalid O/P Signal invalid output. Indicates when all RS-232 signals to the IC are in the invalid range.
Signal-to-Noise Ratio Signal-to-Noise Ratio, the ratio of the amplitude of the desired signal to the amplitude of noise signals at a given point in time. The larger the number, the better. Usually expressed in dB.
SIM Subscriber identity module
SINAD Signal-to-noise and distortion ratio: The RMS value of the sine wave f(IN) (input sine wave for an ADC, reconstructed output sine wave for a DAC) to the RMS value of the converter noise from DC to the Nyquist frequency, including harmonic content. It is typically expressed in dB (decibels).
SLBI System loopback input
SLIC Subscriber-Loop-Interface-Circuit: A telephone line interface.
Smart Battery A battery with internal circuitry that provides level of charge status to the host system.
Smart Phone A phone with a microprocessor, memory, screen, and built-in modem. The smart phone combines some of the capabilities of a PC in a handset device and typically include Internet connectivity.
Smart Signal Conditioner Signal conditioner that is programmable or has a flexible architecture to allow it to accomplish sophisticated signal transformations and corrections.

System Management Bus: A 2-wire serial-interface standard developed by Intel.

Learn More: Comparing the I²C Bus to the SMBus

See Also: I²C


1. Surface Mount Device (SMD): An electronic component that mounts on the surface of a printed circuit board (as opposed to "through-hole" components which have pins that are inserted into holes). SMDs typically allow more components per square centimeter of PC board, but their scale is such that hand assembly and prototyping may be difficult.

2. Standard Military Drawing (SMD): A U.S. government program for standardized MIL-STD-883 product specifications, to simplify military procurement. Sponsored by the DSCC (Defense Supply Center, Columbus).

Learn More:

SMPS Switch-Mode Power Supply
SMR Specialized Mobile Radio: Indicates the 896MHz to 901MHz band (800MHz band), which uses two paired 25kHz channels, and the 935MHz to 940MHz band (900 MHz band), which uses two paired 12.5kHz channels. Ten 20-channel blocks have been allocated in these frequency bands by the FCC. 900MHz SMR is primarily used for radio dispatch, paging, and wireless data communications.

A snubber is a device which suppresses voltage transients.

Learn More: Snubber Circuits Suppress Voltage Transient Spikes in DC-DC Flyback Converter Supplies

See Also: Inductive Kickback

SO Small outline (a package type).
SOC State of change

Also see:

Soft Start

Soft start is a feature in some switching power supplies that limits the startup inrush current at initial startup.

SOHO Small Office/Home Office: Businesses that are either run from home or a from a small office. Software and hardware companies sometimes promote products as suitable for the SOHO market.
SOIC Small outline integrated circuit, a packaging technology.
Solid State A solid state device or circuit is one that relies on semiconductors rather than mechanical or vacuum tube circuits.
SONET Synchronous Optical Network: A North American standard for transmission in synchronous optical networks. It defines a family of rates, formats, interfaces, transport options, and maintenance capabilities. The minimum rate for SDH is 155Mbps.
SOT Small outline transistor
Space Diversity In radio systems, Space Diversity transmits a signal on multiple propagation paths.
SPC Statistical process control
SPCR Service Control Peripheral Register
SPDR Service Control Data Register
Single-pole/double-throw switch
A switch with three leads, one of which is common. The common lead can connect to one or the other leads exclusively.
SPFP Signal power functional part
SPI Serial Peripheral Interface. A 3-wire serial interface developed by Motorola.

Simulation program with integrated circuit emphasis

Learn More: SPICE Models

See Also: Circuit Simulator

Spread Spectrum

Spread-Spectrum is a technology that modulates a signal over many carrier frequencies at once.

This method can be used to make transmissions more secure, reduce interference, and improve bandwidth-sharing.

Spread-spectrum techniques can also be used to reduce electromagnetic interference by dithering the clock frequency so emissions are no longer concentrated at one frequency.

Learn More:

See Also:

SPST Single-pole/single-throw switch
Spurious-Free Unwanted frequencies are not present.
SQC Statistical quality control: Use of statistical methods to measure and improve the quality of manufacturing processes and products. The term "statistical process control" is often used interchangably.
SR Slew rate
SRAM Static RAM: RAM that does not require a clock to retain its contents.
SRF Self-resonant frequency
SS Soft-start; sample size
SSC Smart signal conditioning
SSOP Shrink small-outline package
Star Ground A pcb layout technique in which all components connect to ground at a single point. The traces make in a "star" pattern, emanating from the central ground.
Star Point A point from which all traces leave in a "star" pattern in pcb layout.
STB A "set top box," or STB, is a generic name for an electronic interface between a cable television or satellite signal and video display and recording devices. Typically a box that can be placed atop the television set (hence the name), it can have many functions, including acting as a tuner, decoding digital or analog television signals, removing encryption, and allowing the purchase of pay-per-view channels. Maxim offers a range of products for STB designers.

STC 1. Silicon Timed Circuit: A circuit that produces a delayed version of the input signal. Also known as a delay line.

Also See: Silicon Timed Circuits: Frequently Asked Questions

2. System Timing and Control: Clock generation and distribution systems and components. May include the means for clock control such as spread-spectrum clock generation for EMI reduction, skew rate control, rate dividers, rate control, width, delay, and phase adjustment.

Also See: Clock Generation and Distribution product line page.

Step-Up DC-DC A switch-mode voltage regulator in which output voltage is higher than its input voltage.

See application note 660, "Regulator topologies for battery-powered systems."
Strobe A pulse used for timing and synchronization.
Superheterodyne Receiver A radio receiver that combines a locally generated frequency with the carrier frequency to produce a lower-frequency signal (IF, or intermediate frequency) that is easier to demodulate than the original modulated carrier.
Swallow Counter

The Swallow Counter is one of the three building blocks (swallow counter, main counter, and dual-modulus prescaler) that constitute the programmable divider commonly used in modern frequency synthesizers.

The swallow counter is used to control the dual-modulus prescaler which is set to either N or (N+1). At the initial reset state, the prescaler is set to a divide ratio of (N+1), but the swallow counter will change this divide ratio to N when it finishes counting S number of cycles.

The Swallow Counter gets its name from the idea that it "swallows" 1 from (N+1) of the dual-modulus prescaler.

SWAP Shared wireless access protocol
Switch Mode Uses a switching transistor and inductor to control/regulate the charging voltage/current.
Switched Capacitor Circuit A circuit methodology, typically implemented in CMOS integrated circuits, that uses clocked switches and capacitors to transfer charge from node to node such that a resistor function is realized. The effective resistance is governed by capacitor size and switching clock frequency.
Switching Controller

What is a Switching Controller?

A switching controller is an IC that controls the timing of the switching of a power transistor, usually a FET, used in a switching regulator. In some switching regulators, the FET is a discrete component, external to the controller, while in others, the FET is located in the same IC as the switching controller. The switching controller monitors the output of the switching regulator, as part of a feedback control loop, to ensure the output is kept constant under normal operating conditions.

Related Page:

Switching Regulator

What is a Switching Regulator?

A switching regulator is a circuit that uses a power switch, an inductor, and a diode to transfer energy from input to output. The power switch, usually a Field Effect Transistor (FET), is turned on and off by a switching controller IC that monitors the output of the switching regulator in a feedback control loop. This ensures that it maintains a constant output under normal operating conditions. In some switching regulators, the FET is a discrete component, external to the switching controller. In other versions, the FET and controller are in the same IC. 

The basic components of the switching circuit can be rearranged to form a step-down (buck)converter, a step-up (boost) converter, or an inverter (fly back). These designs are shown in Figures 1, 2, 3, and 4 respectively, where Figures 3 and 4 are the same except for the transformer and the diode polarity.

Figure 1. Buck converter topology.
Figure 1. Buck converter topology.

Figure 2. Simple boost converter.
Figure 2. Simple boost converter.

Figure 3. Inverting topology.
Figure 3. Inverting topology.

Figure 4. Transformer flyback topology.
Figure 4. Transformer flyback topology.

Related Pages:

Why Use a Switching Regulator instead of a Linear Regulator?

Switching regulators offer three main advantages compared to linear regulators. First, switching efficiency can be much better. Second, because less energy is lost in the transfer, smaller components and less thermal management are required. Third, the energy stored by an inductor in a switching regulator can be transformed to output voltages that can be greater than the input (boost), negative (inverter), or can even be transferred through a transformer to provide electrical isolation with respect to the input.

Given the advantages of switching regulators, one might wonder where can linear regulators be used? Linear regulators provide lower noise and higher bandwidth; their simplicity can sometimes offer a less expensive solution. There are, admittedly, disadvantages with switching regulators. They can be noisy and require energy management in the form of a control loop that requires a switching controller. Fortunately, the solution to these control problems is integrated in modern switching controller IC’s.

Maxim Switching Regulators Diagrams

Ultra Low Noise and Ripple Boost Regulator.
Ultra Low Noise and Ripple Boost Regulator.

Synchronous Buck Converter.
Synchronous Buck Converter.

24V, 300mA, Buck Converter.
24V, 300mA, Buck Converter.

SWT Set watchdog timeout
Synchronous Digital Hierarchy Synchronous Digital Hierarchy, SDH: The ITU-TSS International standard for transmitting information over optical fiber.
Synchronous Rectification In switch-mode power supplies, the "steering" diode is replaced or paralleled with a FET switch to reduce losses and thereby increase efficiency. The FET is off during the inductor charge cycle, and then turned on as the inductor discharges into the load.
System on a Chip A System on a Chip (SoC) integrates most of a system's elements on a single integrated circuit (chip). It typically combines a microprocessor core along with interface elements and analog and mixed signal functions.
T/H Track/hold
T/R Transmit/receive
T1 T1 is standard for digital transmission in the United States. It is a digital transmission link with a capacity of 1.544Mbps. T1 uses two pairs of normal twisted wires, the same as found in most residences. T1 normally handles 24 voice conversations, each one digitized at 64kbps. With more advanced digital voice encoding techniques, T1 can handle more voice channels.
T3 A type of data connection capable of transmitting a digital signal at 44Mbps. T3 lines are often used to link large computer networks, such as those that comprise the Internet.
Tachometer A transducer used for measuring the rate of revolution of a shaft.
TAD Total accumulated discharge (mA-hr)

In a potentiometer, taper refers to how the resistance varies as the pot's armature is rotated (or, for a slide pot, as its wiper slides; or for a solid state pot like the DS1802, as its input voltage is varied).

For a pot with a linear taper, the resistance varies linearly as the wiper moves.

For a pot with a logarithmic (log) taper, the resistance varies logarithmically with the wiper's motion. When used in an amplifier circuit, the output varies slowly as the pot is operated at the low end and varies more and more rapidly as the pot is operated toward the high end.

This is also called an audio taper because it is most commonly used for audio volume controls. The ear responds logarithmically (each doubling in signal is perceived as an equal step in volume). The ear is more sensitive to changes at lower volumes, so an audio volume control varies the signal slowly at lower settings and more rapidly at higher settings. The net effect is that the sound seems to vary smoothly through the pot's range.

The perceived volume is subjective and fairly imprecise, so an approximation may be used instead of a true log pot.

Learn More:

TC Temperature coefficient; thermocouple; TURBOCHARGE (control bit)
TCP/IP Transmission Control Protocol/Internet Protocol: The protocols or conventions that computers use to communicate over the Internet.
TCXO Temperature Compensated Crystal Oscillator: A crystal oscillator that includes circuitry that compensates for temperature variations, to maintain a more constant frequency.
TDD Time Division Duplex, the second variation of WCDMA especially suited to indoor environments where there is a need for high traffic density.
TDM Time Division Multiplexing, a scheme in which numerous signals are combined for transmission on a single communications line or channel. Each signal is broken into many segments, each having very short duration.
TDMA Time Division Multiple Access: A method of digital wireless-communications transmission. TDMA allows many users to access (in sequence) a single radio-frequency channel without interference, because it allocates unique time slots to each user within each channel.
TDMoP TDMoP (TDM over Packets), or TDMoIP (TDM over IP), is the implementation of TDM over a packet-switching network. TDMoIP is a trademark of RAD Communications.


Time-delay relay
Time-domain reflectometry
TDSCDMA Chinese Third Generation (3G) telecommunications standard. China's government allocated three frequency bands: 1880MHZ to ~1920MHz, 2010MHz to ~2025MHz, and 2300MHz to ~2400MHz.
TEC A thermoelectric cooler (TEC) is a small cooling device that relies on a Peltier junction. Composed of two conductors made of different materials, a Peltier junction (discovered in 1833 by J.C. Peltier) acts as a heat pump which can cool or warm when current is passed through it.

The small size of the TEC allows precision thermal control of individual components such as fiber optic laser drivers, precision voltage references, or any other temperature critical device. Temperature-critical components are integrated with a TEC and a temperature monitor into a single thermally-engineered module.

A "thermoelectric controller" (also abbreviated TEC) is an electronic circuit that controls the current that drives the junction. These can be quite sophisticated. Many can drive a positive or negative current (so they can heat or cool), use PWM for efficiency, and incorporate control to regulate the amount of current. Examples of such circuits are linked below.

See: App Note 3318, HFAN-08.2.0: Thermoelectric Cooler (TEC) Control.

Television A system for transmitting picture and sound over a distance, primarily via the standards for NTSC, PAL, or HDTV.

See: Video Basics

Tempco Temperature coefficient
Temperature The average kinetic energy of the atoms or molecules of a body or substance, perceived as warmth or coldness. Measured in degrees Fahrenheit, Celsius, or Kelvin.

See: Maxim's full line of thermal management integrated circuits.

Temperature Comparator An integrated circuit with a digital output that indicates whether a measured temperature is above or below a predetermined threshold.
Temperature Sensor

Temperature sensor that uses an external diode-connected transistor as the sensing element to measure temperatures external to the sensor (for example, on a circuit board or on the die of a CPU). Generally produces a digital output.

Learn More: Temperature Sensor ICs

Temperature Switch A circuit that opens and closes a conductive path based on temperature.
Tesla Tesla (abbreviated T) is a measure of magnetic flux density (B-field), named for engineer and inventor Nikola Tesla.
TFT Thin-film transistor
THB Temperature/humidity bias

Total Harmonic Distortion (THD) is a measure of signal distortion which assesses the energy that occurs on harmonics of the original signal. It is specified as a percentage of the signal amplitude.

As an example, if a 12kHz signal is applied to the input, THD would look at energy on the output occurring at 24kHz, 36kHz, 48kHz, etc. and compare it to the energy occurring at 12kHz.

Learn More: THD Test Circuit Eliminates the Need for External Filters

See Also:


Total Harmonic Distortion Plus Noise (THD+N) is the sum of the two most important distortion components.

THD is the distortion that occurs on harmonics of the original signal -- it is correlated with the signal. Noise is the more random, uncorrelated distortion. THD+N is their sum.

Thermal Control Circuit Circuit to monitor and control the temperature of something. For example the integrated temperature controller in Intel's processors.
Thermal Management The use of various temperature monitoring devices and cooling methods, such as forced air flow, within a processor or FPGA-based system, to control overall temperature of ICs and internal cabinet temperatures.
Thermal Monitor The integrated thermal control system used in Intel's processor devices.
Thermal Resistance

Thermal resistance is a measurement of a material’s or a component’s resistance to heat flow. It is the reciprocal of thermal conductance, which is the ability to conduct heat.

Thermal resistance is used in PCB circuit design to measure a package’s heat dissipation and avoid overheating.

There are two values related to thermal resistance that refer to a material’s ability to conduct heat versus a component’s ability to conduct heat: specific thermal resistance and absolute thermal resistance.

How is thermal resistance measured?

Specific thermal resistance (Rλ) is a material constant, measured in K∙m/W or ft2∙h∙oF/Btu, that is useful for comparing materials. It is the reciprocal of the material’s thermal conductivity, and is the absolute thermal resistance per unit area. An R-value is the specific thermal resistance, given in British units of degree Fahrenheit square-foot hour per British thermal unit (ft2∙h∙oF/Btu). For example, a thermal resistance given as R-1 means 1 ft2∙h∙oF/Btu. When using the SI units of kelvin meters per watt K∙m/W, this value is denoted as the RSI-value.

Absolute thermal resistance (Rθ), measured in kelvins per watt (K/W) or degrees Celsius per watt (oC/W), is a property of a determined quantity of a material. Once a material and size have been chosen, absolute thermal resistance is the measure of that component’s ability to resist heat flow. Absolute thermal resistance is an extensive property, meaning it depends on the amount of the material.

Thermal resistance is an important value in PCB circuit design to prevent overheating. IC manufacturers specify a device’s junction-to-ambient thermal resistance (θJA), which is a measurement of absolute thermal resistance and is usually given in oC/W. Other values that are sometimes used are junction-to-case thermal resistance (θJC) and case-to-ambient thermal resistance (θCA). See our tutorials on how to measure junction-to-ambient thermal resistance, and for more on θJA, θJC, and θCA.

Learn More:

Thermal Shutdown Deactivating a circuit when a measured temperature is beyond a predetermined value.
THERMDA Thermal Diode Anode pin on AMD and Intel processors.
THERMDC Thermal Diode Cathode pin on AMD and Intel processors.
Thermistor A temperature-dependent resistor with a high temperature coefficient, usually composed of sintered semiconductor material.
Thermochron A Thermochron device measures and records (logs) temperature. (Thermochron is a trademark of Maxim Integrated.)
Thermocouple A temperature sensor formed by the junction of two dissimilar metals. A thermocouple produces a voltage proportional to the difference in temperature between the hot junction and the lead wire (cold) junction.
Thermostat Circuit that indicates whether a measured temperature is above or below a particular temperature threshold or trip point. Used for thermal protection and simple temperature control systems.
THERMTRIP# Pin name of the Thermal Trip digital output on Intel Pentium processors. The pin is asserted at a nominal die temperature of 135 degrees-C.
THERMTRIP_L Pin name of the thermal trip output pin of AMD processors. The pin is asserted at a nominal die temperature of 125°C.

A three-state, or Tri-State™, output has three electrical states: One, zero, and "Hi-Z," or "open."

The hi-Z state is a high-impedance state in which the output is disconnected, leaving the signal open, to be driven by another device (or to be pulled up or down by a resistor provided to prevent an undefined state).

High-impedance schemes such as three-state are commonly used for a bus, in which several devices can be selected to drive the bus.

Tri-State™ is a trademark of National Semiconductor.

See Also: Open-Drain

Through-Hole A method for mounting components on a printed circuit board (PCB) in which pins on the component are inserted into holes in the board and soldered in place.
Time Diversity In radio systems, Time Diversity spreads a signal across multiple channels by placing multiple versions of the signal in different time slots.
Time of Flight

Time of flight is the measurement of time taken to travel a distance in order to determine distance, speed, or properties of the medium. Time for a signal to reflect off an object is often measured to determine the object’s location.

How is time of flight calculated?

Consider a time of flight example consisting of a light and sensor on one end and an object on the other. A pulse of light travels to the object, is reflected off of it, and returns to a sensor right next to where the light originated:

Time of flight example

By definition, speed (s) is the distance travelled (d) divided by the time taken (t): s=d/t

The speed of light is referred to as c. The total distance travelled is the distance from the sensor to the object (x) plus the trip back from the object to the sensor (also x), so the total distance travelled is 2x.

Rearranging the equation for speed and inserting our values for distance and speed, we get x=ct/2

Since the speed of light is a known value (approximately 300 million m/s), by measuring the time it takes for light to travel to an object and back, we’re able to measure how far away the object is. This is the basic idea behind a time-of-flight camera.

Using light to measure distance is a common application, but this same idea can be generalized to any object or wave travelling at any speed, through any medium, and the source and sensor do not need to be next to each other. The time of flight principle could then be used to determine properties of the medium, or measure an unknown velocity travelling a known distance.

Is LiDAR time of flight?

LiDAR (light detection and ranging) uses ToF by emitting laser light pulses in multiple directions and measuring return time in order to detect objects. In addition to measuring return time, LiDAR may also measure the energy of the reflected light in order to create the detail in its distance map of the surrounding objects.

Learn More:

Tin Whiskers

Tin whiskers (also called Sn whiskers or metal whiskers) are microscopic, conductive, hair-like crystals that emanate spontaneously from pure tin (especially electroplated tin) surfaces.

Whiskers form primarily on elemental metals, but have also been found on alloys. Crystals can form in any environment. The actual mechanism for their formation is not well understood.

Tin-lead (SnPb) finishes prevent tin whiskers. Maxim offers an SnPb solution for customers requiring a non-RoHS finish. It is available for virtually all lead-free products.

Tin whiskers are not dendrites. Dendrites are fern-like and grow on the surface of the metal in an environment with moisture present. Tin whiskers tend to grow orthogonally from the surface.

Learn More:

TINI® is Maxim's trademark for its family of highly integrated solutions for the consumer electronics market. The family includes ICs which integrate disparate functions to achieve advantages in board space. Examples include:
  • TINI Power SoCs integrate all the functional blocks needed to power applications and baseband processors, along with mixed-signal functions like audio, battery management, and touch-screen control. These Power SoCs allow mobile platform system designers to cut their analog footprint in half.
  • TINI Audio Codecs (MAX98089, MAX98095) combine multiple high-performance audio blocks with Maxim's proprietary FlexSound® processor. These audio codecs let designers overcome integration challenges in mobile products while delivering the best audio experience.
  • TINI Touch-Screen Controller SoCs (MAX11871) integrate the industry's highest SNR capacitive-touch analog front-end (AFE), a MAXQ® CPU for full backend processing, and a custom DSP coprocessor. The integration of a super-narrowband AFE provides breakthrough immunity to AC charger and LCD noise without any external components.
TINI is a registered trademark of Maxim Integrated
Note: Tiny Network Interface circuits are now called MxTNI.
TLA Three-Letter Acronym.
Totem Pole A standard CMOS output structure where a P-channel MOSFET is connected in series with an N-Channel MOSFET and the connection point between the two is the output. The P-FET sits on top of the N-FET like a "totem pole." Both gates are driven by the same signal. When the signal is low, the P-FET is on; when the signal is high, the N-FET is on. This creates a push-pull output using just two transistors.
TQFN Thin version of the QFN package (the JEDEC "W" option) 0.8mm thick.
TQFP Thin quad flat pack
Transceiver A device that contains both a transmitter and receiver.

Common misspellings: Transciever, Tranceiver, Transeiver, Transiever, Tranciever, Transcever.


Transconductance The gain of a transconductance amplifier (an amp in which a change in input voltage causes a linear change in output current). The basic gain of vacuum tubes and FETs is expressed as transconductance. It is represented with the symbol gm.

The term derives from "transfer conductance" and is measured in siemens (S), where 1 siemens = 1 ampere per volt. It was formerly measured as "mho" (ohm spelled backwards).

Transconductance Amplifier

An amplifier that converts a voltage to a current. Also known by several other terms (see synonym list). One synonym is OTA, or operational transconductance amplifier, a term that marries the terms transconductance amplifier and operational amplifier.

The term derives from "transfer conductance" and is measured in siemens (S), where 1 siemens = 1 ampere per volt. It is represented with the symbol gm. The basic gain of vacuum tubes and FETs is expressed as transconductance.

Learn More: Transimpedance Amplifier Buffers Current Transformer

See Also: Transimpedance Amplifier

Transducer Electronic Data Sheet A Transducer Electronic Data Sheet, or TEDS, is a method for plug-and-play sensor and transducer hook-up in which the sensor's calibration information is stored within the device and downloaded to the master controller when requested. A standardized TEDS specification is being developed by the IEEE, as IEEE P 1451.4.
Transfer Transfer refers to the amount of data transferred across a digital interface, exclusive of any extra bits used to encode the data.

The number of data transfers is less than the number of bits transmitted when encoded data has more bits than the raw data. As an example, a PCIe serial bus uses 10 bits to encode eight data bits. (Extra bit space may be used to encode a clock, error-detection redundancy, etc.)

Data rates are commonly expressed in transfers per second, gigatransfers per second (GT/s) and megatransfers per second (MT/s).


An inductive electrical device for changing the voltage of alternating current.

A transformer consists of two magnetically coupled coils. Alternating current in one (called the "primary") creates a changing magnetic field which induces a current in the second coil (the "secondary"). A core made of iron or ferrite generally connects the two coils, but higher frequency devices can work without a ferrous core.

Transformers have two primary functions: Voltage transformation and isolation:

  • The voltage of the secondary can be higher or lower than the voltage that drives the primary and is determined by the ratio of turns of wire in the two coils.
  • Isolation refers to the fact that the coils are connected only by a magnetic field, so they can be independent of a common ground.

Primary applications are for power and for signal isolation / impedance transformation.

An autotransformer is a transformer with a single coil with intermediate "taps" to effect the changed outgoing voltages. They do not provide isolation.

Transformer capacity is rated in kilovolt-amps (KVA): The volts x amps / 1000.

Learn More: Transformer Drivers

Transient Intermodulation Distortion

Transient intermodulation distortion (TIM) occurs in amplifiers that employ negative feedback when signal delays make the amplifier incapable of correcting distortion when exposed to fast, transient signals.

Transimpedance Amplifier

A transimpedance amplifier is an amplifier which converts a current to a voltage. It is a familiar component in fiber-communications modules.

The unit for transresistance is the ohm.

Learn More: Transimpedance Amplifier Buffers Current Transformer


A basic solid-state control device which allows or disallows current flow between two terminals, based on the voltage or current delivered to a third terminal.

Usually built from silicon but can be constructed from other semiconductor materials. There are two major types: The field-effect transistor (FET) and the bipolar junction transistor (BJT).

The first transistor was invented in 1947 at Bell Labs by Michael John Bardeen, Walter Brattain and William Shockley.


A circuit that accepts signals or data in and translates them into a form that can be sent across a medium (transmitted), usually over a distance. The medium can be wireless or wired.


  • A radio transmitter that modulates the signal on a carrier and transmits it over the airwaves
  • An ultrasonic transducer that sends the signal over ultrasound frequencies
  • A line driver that drives a backplane
  • A circuit that drives an interface (e.g., USB, serial, LVDS)
  • A fiber optic device that emits light pulses
TS 16949 TS 16949 is an ISO Technical Specification that aligns previous American (QS-9000), German (VDA6.1), French (EAQF) and Italian (AVSQ) automotive quality systems standards within the global automotive industry. Together with ISO 9001:2000, ISO/TS 16949:2002 specifies the quality system requirements for the design/development, production, installation and servicing of automotive related products.
TSOC Thin small-outline C-lead
TSOP Thin small-outline package
TSSM Temperature sensor and system monitor
TSSOP Thin shrink small-outline package
TTC Temperature conversion sample time
TTFC Time remaining to full charge
TTIMD Two-tone intermodulation distortion
TTL Transistor-to-transistor logic
Tubular Motor A tubular motor is an electric motor embedded in a cylindrical form factor. They are typically used for window shades and blinds, projection screens, awnings, roller doors, etc.
TUE Total unadjusted error
TVM Test vector monitor
TVS Transient Voltage Suppressor: Semiconductor device designed to protect a circuit from voltage and current transients. Typically implemented as a large silicon diode operating in avalanche mode to absorb large currents quickly.
Tweak Tweak (or sometimes, "tweek") means to make small adjustments to a system to improve its performance.
Tx Transmit
uA Microampere, or microamp: A millionth of an Ampere. Ampere is the basic unit for measuring electrical current.

Often written as uA, but the u is a plain-text substitute for the Greek letter mu.


Universal Asynchronous Receiver-Transmitter: An IC that converts parallel data to serial, for transmission; and converts received serial data to parallel data.

Learn More: UARTs

UBM Underbump metal
UHF Filter Ultra High Frequency filter
UI Unit interval (used to describe jitter generation); user information; user interface
ULTRA160 A SCSI interface label, where 160 refers to the maximum reliable throughput in megabits per second.
UMTS UMTS (Universal Mobile Telecommunications System) is a third-generation cellular standard based on the GSM standard and developed by the 3rd Generation Partnership Project (3GPP).
Uninterruptible Power Supply An uninterruptible power supply (UPS) is a device that maintains power in the event of a failure. A UPS commonly includes a battery that is kept charged and ready. When power fails, the battery supplies power, as long as it lasts. When the battery fails, a UPS may contain circuitry that triggers an orderly shutdown.

An uninterruptible power supply may also provide line regulation, protecting against voltage variations.

UniqueWare A unique identification technique
UniqueWare Serialized A factory-programming service for 1-Wire EPROM chips with customer-specified data. Service provides one serialization file for customers to create identifiers in silicon.

An upconverter is a device which provides frequency conversion to a higher frequency, e.g., in digital broadcast-satellite applications.

URL Uniform/universal resource locator — web address, eg

Universal Serial Bus (USB): A standard port that enables you to connect external devices (such as digital cameras, scanners, keyboards, and mice) to computers. The USB standard supports data transfer at three rates: low speed (1.5MBps), full speed (12Mbps) and high speed (480 MBps).

Mbps=million bits per second.

Learn More: Practical USB Terminology

UV Ultraviolet
UVLO Undervoltage lockout

Ultra-Wideband (UWB) is a communications technology that employs a wide bandwidth (typically defined as greater than 20% of the center frequency or 500MHz).

UWB is usually used in short-range wireless applications but can be sent over wires. Ultra-Wideband advantages are that it can carry high data rates with low power and little interference.

UWB is the modern version of older "impulse" technologies which are generated by very short pulses (impulse waveforms). They were called "carrier-free" or "baseband" because the energy is so widespread in the frequency domain that there is no discernible carrier frequency.

For a crude example, connect a metal file to one terminal of a battery and a wire to the other terminal. Brush the wire across the teeth of the file and note that the electrical noise can be heard on a radio tuned to just about any frequency.

The FCC authorizes UWB between 3.1 and 10.6GHz (but is not likely to approve devices that rely on a file and a wire.)

V-s Volt-second(s)
V/F Voltage-to-frequency

VRMS stands for root-mean-square voltage.

Why is RMS used?

Unlike DC voltages which are constant over time, AC (alternating current) voltages are time varying and sinusoidal in shape. The RMS value of an AC signal is equivalent to the DC voltage that would be required to produce the same heating effect (power). The RMS of mains electricity in the U.S. is 110VRMS and in Europe it is 220VRMS.

How is RMS voltage different to the average voltage?

A sinusoidal signal (Figure 1) alternates between a peak positive and peak negative value once every cycle. Therefore, the average value of the signal is zero, so the average value of the signal is not a useful quantity. The power of an AC signal is used on both the positive and negative cycles. RMS is calculated using the square of signal voltage values at specific points in time. Since squaring eliminates negative numbers, it incorporates the contribution of the negative values. In this way, it is similar to calculating the standard deviation of a set of numbers which have a mean of zero.

sinusoidally varying ac signal vrms

Figure 1. Sinusoidally varying AC signal

What is the relationship between RMS and peak voltage?

The formula that relates VRMS and Vpk is:


 VRMS =  -------


Learn more: Data conversion calculator 

VA Volt ampere(s)
Vcc The supply voltage for a circuit is often given as V plus a double-letter suffix. The double letter is usually related to the lead of the transistors that are commonly connected to that supply or to a resistor that connects to that supply.

Examples: VCC is a positive-voltage supply and the collector terminal of bipolar transistors is connected to the VCC supply or to a load which connects to VCC. VSS connects to the source terminal of a FET, etc.

V+ and V- are also common ways to refer to a supply voltage.


A voltage-controlled oscillator (VCO) is an electronic oscillator whose output frequency is proportional to its input voltage. An oscillator produces a periodic AC signal, and in VCOs, the oscillation frequency is determined by voltage.

How does a voltage-controlled oscillator work?

Oscillators work by transferring energy back and forth from one form to another. One way to do this is with an LC circuit, where energy moves between the inductor (L) and the capacitor (C). The capacitor stores energy in the form of an electric field between its plates and discharges through the inductor, which then stores that energy in the form of a magnetic field. The inductor then charges the other plate of the capacitor and the process starts again, but with current now flowing in the opposite direction. The frequency at which this oscillation occurs is the resonant frequency, which is inversely proportional to √LC.

A voltage-controlled oscillator can be constructed by using a varactor diode as a voltage-controlled capacitor. As the reverse bias voltage across the varactor diode changes, so does its capacitance, and therefore so does its frequency.

What are VCOs used for?

VCOs are an important part of a phase-locked loop (PLL), which is a control system that generates a signal with a fixed relation to the phase of a “reference” signal. PLLs have a wide variety of uses in radio, telecommunications, computers, and other electronic applications. VCOs can also have other uses in frequency and phase modulation, and have applications such as function generators and synthesizers.

Learn More:

VCSEL Vertical cavity-surface emitting laser
VCTCXO Voltage Controlled, Temperature Compensated Crystal Oscillator: A TCXO which offers the ability to control the oscillation frequency with an analog voltage
VCXO Voltage Controlled Crystal Oscillator: An oscillator that uses a crystal to establish its frequency but will vary its frequency as an analog control voltage varies.
VDSL Very High Data-Rate Digital Subscriber Line: A method for delivering high-speed digital services on the standard twisted pair used for voice phone lines. VDSH operates at data rates from 12.9Mbps to 52.8Mbps.
VFD Vacuum Fluorescent Display
VFO Variable-frequency oscillator
VGA Variable-gain amplifier
VLF Very-low frequency
VLIF Very-low intermediate frequency

Very large-scale integration (VLSI) refers to an IC or technology with many devices on one chip. The question, of course, is how one defines "many."

The term originated in the 1970s along with "SSI" (small-scale integration), "LSI" (large-scale), and several others, defined by the number of transistors or gates per IC. It was all a bit silly since improving technology obviously makes numerical definitions meaningless over time. And it varies by industry -- a VLSI analog part is quite different from a VLSI digital logic part or a VLSI memory part.

Eventually, the pundits began trying terms like "ULSI" (ultra-large-scale). Engineers, meanwhile, ignored it all and spent their time building better devices instead of making up new words for them.

The terms LSI and VLSI are now usually used as general terms, referring to a product or technology that subjectively has more devices than typical products in the category. Maxim has observed a technical trend in analog and mixed signal toward increasing complexity. Many of our parts include complex control, such as the MAXQ microcontroller core, with many times more devices than most analog parts.

VME VERSAmodule Eurocard, or VMEBus, a microcomputer bus. Standardized in IEC 821, IEEE 1014-1987 and ANSI/VITA 1-1994.
VoIP Voice over Internet Protocol: Method for transmission of voice (or fax) calls over the Internet.
Volt Volt (or Volts): Unit of measure for electromotive force (EMF), the electrical potential between two points. An electrical potential of 1 volt will push 1 ampere of current through a 1-ohm resistive load.

Using a common plumbing analogy, voltage is similar to water pressure and current is analogous to flow (e.g. liters per minute).

In equations, the symbol E is often used (as in: E = IR). V is the symbol for the unit of measure, Volt.

Volt-Ampere A volt-ampere (VA) is the voltage times the current feeding an electrical load. A kilovolt-ampere (kVA) is 1000 volt-amperes.

Electrical power is measured in watts (W): The voltage times the current measured each instant. In a direct current system or for resistive loads, the wattage and VA measurements will be identical. But for reactive loads, the voltage and current are out of phase and the volt-ampere spec will be greater than the wattage.

For determining power, watts are appropriate. For determining capacity for the driving circuits (circuit breakers, wiring, and uninterruptible power supplies, for instance), VA is appropriate.

Voltage Divider

A voltage divider is an electrical circuit whose output voltage is smaller than its input (Figure 1).

voltage divider circuit

Figure 1 Voltage Divider Circuit

The term “voltage divider” relates to how the circuit works. It comprises two series resistors (R1 and R2) and an input voltage source (Vin) as shown in Figure 1. As determined by Ohm’s Law, the output voltage is ‘divided’ down by the ratio of the two series resistors according to the following formula:

voltage divider resistor equation formula

A voltage divider in which the value of the resistor(s) is variable is called a potentiometer.

Although it a quick and simple way to create a smaller voltage level from a fixed voltage source (e.g. battery), the voltage divider is inefficient for practical use for a number of reasons:

A voltage divider wastes current from the input voltage source to generate the output voltage. An ideal voltage source should only deliver current to the load.

While increasing the size of the resistors will reduce the amount of wasted current, this also increases the output resistance of the circuit meaning not all of the output voltage is transferred to the load. An ideal voltage source should have zero output resistance, so that all of the voltage is transferred to the load.  

For practical applications, the output of a voltage divider circuit must first be buffered by another circuit before use or a more efficient type of voltage reference should be chosen.

Learn More:

Voltage Doubler A capacitor charge pump circuit which produces an output voltage which is twice the input voltage.
Voltage Identification Digital Voltage Identification Digital, or VID, is a circuit concept developed to provide the central processing unit (CPU) of a computer with the appropriate supply voltage. Instead of having a power supply unit generate some fixed voltage, the CPU uses a small set of digital signals, the VID lines, to instruct an on-board power converter of the desired voltage level.
Voltage Regulator A circuit which is connected between the power source and a load, which provides a constant voltage despite variations in input voltage or output load.
VOM Volt-Ohm meter
Vp-p Peak-to-peak voltage
VPU VPU is a symbol for the pull-up voltage specification (or "Pullup Supply Voltage").
VRD Voltage Regulator Down, an Intel standard for voltage regulators which are "down" on the mother board.
VRM Voltage Regulator Module: An Intel Standard for switching regulator modules.
VS VCO_SEL (control bit)
VSIA Virtual Socket Interface Alliance

VSWR (Voltage Standing Wave Ratio) is a measure of how efficiently radio-frequency power is transmitted from a power source, through a transmission line, into a load (for example, from a power amplifier through a transmission line, to an antenna).

In an ideal system, 100% of the energy is transmitted. This requires an exact match between the source impedance, the characteristic impedance of the transmission line and all its connectors, and the load's impedance. The signal's AC voltage will be the same from end to end since it runs through without interference.

In real systems, mismatched impedances cause some of the power to be reflected back toward the source (like an echo). Reflections cause destructive interference, leading to peaks and valleys in the voltage at various times and distances along the line.

VSWR measures these voltage variances. It is the ratio of the highest voltage anywhere along the transmission line to the lowest. Since the voltage doesn't vary in an ideal system, its VSWR is 1.0 (or, as commonly expressed, 1:1). When reflections occur, the voltages vary and VSWR is higher -- 1.2 (or 1.2:1), for instance.


VSWR is the voltage ratio of the signal on the transmission line:

VSWR = |V(max)| / |V(min)|

where V(max) is the maximum voltage of the signal along the line, and V(min) is the minimum voltage along the line.

It can also be derived from the impedances:

VSWR = (1+gamma)/(1-gamma)

where gamma (gamma) is the voltage reflection coefficient near the load, derived from the load impedance (ZL) and the source impedance (Zo):

gamma = (ZL-Zo)/(ZL+Zo)

If the load and transmission line are matched, gamma = 0, and VSWR = 1.0 (or 1:1).

Learn More: Tutorial 5432: Voltage Standing Wave Ratio Definition and Formula

VU Volume unit
W Watt (W) is the unit for measuring power. In physics terms, one watt is one Joule of energy transferred or dissipated in one second. Electrical power is calculated as:

  Watts = Volts x Amps x Power Factor

The power factor can be disregarded for DC circuits or for AC circuits with a resistive load (it is 1 in those situations).

W/Dog O/P Flag Watchdog output flag
Wafer Semiconductor manufacturing begins with a thin disk of semiconductor material, called a "wafer." A series of processes defines transistors and other structures, interconnected by conductors to build the desired circuit.

The wafer is then sliced into "dice" which are mounted in packages, creating the IC.

Wafer Fab Semiconductor processing facility which turns wafers into integrated circuits. A typical wafer fab employs a series of complex steps to define conductors, transistors, resistors, and other electronic components on the the semiconductor wafer. Imaging steps define what areas will be affected by subsequent physical and chemical processes.
WAN Wide Area Network: Any Internet or network that covers an area larger than a single building.
Watchdog A feature of a microprocessor supervisory circuit that monitors software execution in a microprocessor or microcontroller. It takes appropriate action (assert a reset or nonmaskable interrupt) if the processor gets stuck in an infinite execution loop.
Wb Weber: A measure of magnetic flux.
WB-CDMA Wideband Code Division Multiple Access, a standard derived from the original CDMA. WB-CDMA is the third-generation (3G) mobile wireless technology capable of supporting voice, video, and data communications up to 2Mbps.
WDI Watchdog input
WDPO Watchdog pulse output
WE Write enable
WHDI WHDI (Wireless Home Digital Interface) is a standard that enables wireless delivery of uncompressed HDTV throughout the home with video rates of up to 1080p in the 5GHz unlicensed band.

The WHDI group claims consistent picture quality equivalent to wired HDMI, low latency, multiroom availability, and low power consumption.

See: WHDI Products Overview.
Wideband A classification of the information capacity or bandwidth of a communication channel. Wideband is generally understood to mean a bandwidth between 64kbits/s and 2Mbit/s.
WiMax WiMax (Worldwide Interoperability for Microwave Access) is a "last mile," broadband, wireless access mechanism which can potentially replace DSL and Cable Modem. Defined by the IEEE 802.16 standards.

While Wi-Fi (802.11) covers a small area with a radius of a few hundred meters, WiMax (802.16) can cover up to 6 miles with only one base station.

Also known as WirelessMAN, for "Wireless Metropolitan Area Networks."

Window Comparator A device, usually consisting of a pair of voltage comparators, in which output indicates whether the measured signal is within the voltage range bounded by two different thresholds (an "upper" threshold and a "lower" threshold).
Window Watchdog

A special subset of the watchdog timer feature found on microprocessor supervisory circuits. It is used to monitor software execution and assert a reset or an NMI if the processor gets stuck in a loop. This feature not only looks for periodic transitions on its input within a preprogrammed timeout period, but it also looks to see if there are "too many" transitions within its timeout period (window).

Learn More: The Basics of Windowed Watchdogs


When multiple high-impedance (open-collector or open-drain) output pins are connected to a signal line (e.g. a bus) and the system is designed so no more than one is on, a wired-and signal is achieved. This achieves the equivalent of a logical AND function.

Depending on the signal sense, the function could be seen as a OR, so the term "wired-OR" is sometimes used.

See Also: Hi-Z

Wireless Radio-frequency devices, circuits, or communications methods.
Wireless Sensor Network Wireless Sensor Network, or WSN, is a network of RF transceivers, sensors, machine controllers, microcontrollers, and user interface devices with at least two nodes communicating by means of wireless transmissions.
WLAN Wireless Local Area Network

WLED is a term usually associated with television and mobile phone LCD displays. Although WLED is marketed as being in some way “different” or “superior” to standard LED, WLED, and LED technology are identical, using semiconductor materials. The white light produced is used as a ‘backlight’ for LCD displays and is created by applying an electric field to a blue (or UV) LED and then filtering the emitted light through a material of a different color (e.g., a yellow phosphor). The combination of the light and filter create a white (or almost white) light. In an LCD display, this light is then polarized using arrays of many liquid crystals, operating under the influence of variable electric fields, to create images on a screen.

What is the Difference Between WLED and OLED?

OLED (organic light emitting diode) technology uses organic (carbon-based) materials, instead of semiconductor (e.g., silicon or indium) materials used by standard LEDs. Each pixel of an OLED display comprises a red, green, and blue diode which emit light when a voltage is applied to them. Each diode can be switched on and off in different combinations and with different intensities to create images on a screen.

What are the Relative Advantages and Disadvantages of OLED/WLED?

The main advantage of OLED technology is that it allows displays to be much thinner (up to 10x) than displays made using LCD technology (with WLED backlight). Another important advantage is that because OLED displays do not need a backlight, they consume less power. This is critical for battery-powered displays (such as smartphones) as it means the battery does need to be charged as often. However, some disadvantages of OLED displays are that they are less water-resistant and the colors they produce deteriorates over time.

WLL Wireless Local Loop: Any method of using wireless communication in place of a wired connection to provide subscribers with standard telephone service.
WR-RD Write-read
Write Protect Any method that keeps data from being over-written. It may be a physical obstacle or a file attribute choice that prevents overwriting.
WTA Wireless Telephony Application: A collection of telephony-specific extensions for call- and feature-control mechanisms that make advanced mobile network services available to end users. WTA essentially merges the features and services of data networks with the services of voice networks.
XAUI Innovation of the 10 Gigabit Ethernet Task Force. XAUI (pronounced "Zowie") is a ten Gigabit/second interface. The "AUI" portion is borrowed from the Ethernet Attachment Unit Interface. The "X" represents the Roman numeral for ten and implies ten gigabits per second. The XAUI is designed as an interface extender, and the interface which it extends is the XGMII, the ten Gigabit Media Independent Interface.
XCO Crystal clock oscillator (XCO): An oscillator that relies on a crystal for its frequency reference. A piezoelectric crystal oscillates at a very stable frequency.
XOR Gate

What is an XOR Gate?

“XOR” an abbreviation for “Exclusively-OR.” The simplest XOR gate is a two-input digital circuit that outputs a logical “1” if the two input values differ, i.e., its output is a logical “1” if either of its inputs are 1, but not at the same time (exclusively). The symbol and truth table for an XOR is shown in Figure 1. The Boolean expression for a two-input XOR gate, with inputs A and B and output X:

Digital XOR Gate Symbol

Figure 1. Symbol and truth table for a digital XOR gate


What is an XOR gate used for?

The XOR gate has many applications in electronic circuits. It is used in simple digital addition circuits which calculate the sum and carry of two (half-adder) or three (full-adder) bit numbers.

XOR gates are also used to determine the parity of a binary number, i.e., if the total number of 1’s in the number is odd or even. The output of the XOR function, which is 1 if the number of 1’s is odd and 0 if the number of 1’s is even, is referred to as a ‘parity’ bit. This result can be used to perform simple error checking on blocks of digital data being transmitted across a communications link. The parity bit is transmitted along with the original block of data. The receiver performs the XOR function on the received data and if the result matches the received parity bit then there is a limited degree of reassurance that a data error (where a 1 became a 0 or vice versa) did not occur during transmission.

XOR gates are a fundamental building block of cryptographic circuits because XOR logic acts as a simple cipher, i.e., performing an XOR of a digitized message with a binary key produces encrypted ciphertext. Performing an XOR of the ciphertext with the same key reproduces the original message.

Learn more:


Y, C, YUV, Y-Pb-Pr, YCbCr, and Y/C (also known as S-video) are terms that refer to video signal components. The black and white (luminance) portion of the video signal is the "Y" component which, when combined with color components, form a complete picture.

The different nomenclatures for the color components reflect different color encoding schemes.

Learn More: Video Basics

See Also:

YIG Yttrium-iron-garnet (YIG) is a ferrimagnetic material used for solid-state lasers and for microwave and optical communications devices.
Zener Diode

A zener diode is a diode manufactured to have a specific reverse-breakdown voltage. Its most common use is as a voltage reference.

When reverse biased through a resistor, a zener diode will allow enough current to establish its specified voltage.

Learn More: Selecting the Optimum Voltage Reference

ZIF Zero Insertion Force: A class of IC sockets which clamp the IC pins (via a small lever on the side of the socket) after insertion, and thus require no downward force on the IC or its pins to insert it into the socket. Especially useful in applications in which repeated insertions subjects the IC or the socket to wear and breakage.
ZIGBEE A standard for short-distance, low-data-rate communications using the frequencies and physical and data layers of the IEEE 802.15.4 PHY specification. Created and maintained by the ZIGBEE Alliance Group.
ZS Zero scale
ZVC Zero voltage crossing
ZVS Zero voltage switching