|Vacuum Fluorescent Display||See VFD|
|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.
|VCIS||See Transconductance Amplifier|
|VCO||Voltage-Controlled Oscillator: An oscillator device in which output frequency is proportional to its input voltage.|
|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.|
|VERSAmodule Europe||See VME|
|VERSAmodule Eurocard||See VME|
|VERSAmodule European||See VME|
|Very High Data-Rate Digital Subscriber Line||See VDSL|
|Very large-scale integration||See VLSI|
|VFD||Vacuum Fluorescent Display|
|VID||See Voltage Identification Digital|
|VLIF||Very-low intermediate frequency|
|VLSI||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.|
|Voice over IP||See VoIP|
|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 Controlled Crystal Oscillator||See VCXO|
|voltage controlled current source||See Transconductance Amplifier|
|Voltage Controlled Oscillator||See VCO|
|Voltage Controlled Temperature Compensated Crystal Oscillator||See VCTCXO|
|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 Output Temperature Sensor||See PWM Temperature Sensor|
|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.|
|Voltage Regulator Module||See VRM|
|Voltage Standing Wave Ratio||See VSWR|
|Voltage Temperature Sensor||See Analog Temperature Sensor|
|Voltage Tripler||See Charge Pump|
|Voltage-Controlled Oscillator||See VCO|
|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||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+)/(1-)
where (gamma) is the voltage reflection coefficient near the load, derived from the load impeadance (ZL) and the source impedance (Zo):
If the load and transmission line are matched, = 0, and VSWR = 1.0 (or 1:1).