Glossary Terms and Definitions Beginning with the Letter I

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I See Ampere
I²C 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—see Comparing the I²C Bus to the SMBus.

For more information, do a site search for I²C to find other I²C articles and products.

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-Link See FireWire
I.M.V.P See IMVP
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

IC Foundry See Wafer Fab
ICA Integrated circuit accumulator
ICR Internal calibration register
ICVS See Transimpedance Amplifier
Ideal Factor See Ideality Factor
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.

IEC connector See IEC
IEC-320 See IEC
IEEE From www.ieee.org: "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.
IEEE 1394 See FireWire
IEEE 802.11g See 802.11g
IEEE 802.15.4 See ZIGBEE
IEEE 802.16 See WiMax
IEEE P 1451.4 See Transducer Electronic Data Sheet
IEEE-1394 See FireWire
IEEE-488 See GPIB
IEEE802.11 See 802.11
IEEE802.11a See 802.11a
IEEE802.11b See 802.11b
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
IHS See Integrated Heat Spreader
IIC See I²C
III-V See Semiconductor
IIP3 Third Order Input Intercept Point: 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.
IIS See I²S
IM See Intermodulation
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.
IMD 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.

Impulse See UWB
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.
In-Rush See Inrush Current
In-Rush Current See Inrush Current
Inductive Kickback 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.
Inductor-Based See DC-DC
Inductor-Based Switcher See DC-DC
Industrial Scientific And Medical See ISM
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.
Infrared See IR
Infrared Data Association See IrDA
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 Back-Off See IBO
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™).

Input Voltage Range See Input CMVR (V)
Inrush See Inrush Current
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 Non-Linearity See Integral Nonlinearity
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 circuit See IC
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.
Integrated Interchip Sound See I²S
Integrated Temperature Sensor See Local Temperature Sensor
Intel Mobile Voltage Positioning See IMVP
Intellectual Property Intellectual Property: Creations of the intellect such as trade knowledge, technical information, and literary or artistic work, including patents, copyrights, and trademarks.
inter-IC bus See I²C
Inter-IC Sound See I²S
Inter-Modulation Distortion See IMD
Inter-Symbol Interference See ISI
Intergrated circuit See IC
Interleave To organize the data sectors on a computer hard disk, so the read/write heads can access information faster.
Intermediate Frequency See IF
Intermod See IMD
Intermodulation 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.
Intermodulation Distortion See IMD
Internal Temperature See Local Temperature
International Electrotechnical Commission See IEC
International Standards Organization See ISO
International Telecommunication Union See ITU
Internet Protocol Standard method for data transfer used on the Internet. Also known as IP or TCP/IP.
Internet Service Provider See ISP
Intersymbol Interference See Jitter
Inverter See Inverting Switching Regulator
Inverters See Inverting Switching Regulator
Inverting Controller See DC-DC Controller
Inverting DC-DC Converter See Inverting Switching Regulator
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 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.
IP See Ingress Protection
IP3 Third-order intercept point
IQ See I/Q
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
ISO/TS-16949 See TS 16949
ISO/TS16949:2002 See TS 16949
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.
IVR See Input CMVR (V)