Electronics glossary — Letter V

57 terms starting with V

Vac

Volts, alternating current.

vacuum evaporation

A process for generating thin films, in which the film material is vaporized and the vapor deposits itself, through openings in a mask, onto a substrate.

Varactor

A p-n junction diode that is designed to act as a voltage controlled capacitance when it is operated under reverse bias

Varactor-tuned Oscillator

An oscillator whose frequency is a function of an externally generated voltage control signal.

variable

A quantity that can assume any of a given set of values.

Varistor

(Variable Resistor) An overvoltage protection device whose resistance decreases during a voltage surge.

VCC

Voltage collector

VCO

Voltage controlled oscillator – An oscillator whose frequency is a function of an externally generated voltage control signal.

Vdc

Volts, direct current.

VDE

Verband Deutscher Elektrontechniker – German organization that sets standards for product safety and noise emissions and test and certifies products to those standards.

VDOP

Vertical DOP

VDSL

very high bit-rate subscriber line

Vector

A mathematical representation that has both magnitude and direction.

Vector Modulator

A modulator that modulates both amplitude and phase.

Velocity of Propagation

The ratio of the speed of a radio frequency wave within a cable or dielectric as compared with the same wave in free space.

Verband Deutscher Elektrontechniker

VDE – German organization that sets standards for product safety and noise emissions and test and certifies products to those standards.

very high frequency

vhf – A Federal Communications Commission designation for the band from 30 to 300 MHz on the radio spectrum.

very-large-scale integration

VLSI. An IC that in complexity contains over 1000 gates or their equivalent.

VESA

Video Electronics Standards Association, is an international standards body for computer graphics founded in 1989 by NEC Home Electronics and eight other video display adapter manufacturers.

VGA

Video Graphics Array refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987, but through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector or the 640×480 resolution itself.

vhf

Very High Frequency. A Federal Communications Commission designation for the band from 30 to 300 MHz on the radio spectrum.

VHSIC

Very high speed integrated circuit. A Department of Defense program to develop exceptionally fast ICs.

Vias

used to connect traces between two or more layers

vibration

(1)A continuously reversing change in the magnitude of a force. (2)A mechanical motion or oscillation about a given point of equilibrium.

Video

The frequency spectrum that corresponds to that of a signal to be displayed in a television or radar system. The video bandwidth is generally considered to extend from DC to several megahertz.

Video Impedance

The video impedance of a detector diode is the low frequency impedance looking into the diode from the video amplifier. The symbol for video impedance is RV. It is essentially the (AC) slope of the diode at the bias level set up by external bias of the RF signal. This impedance is affected by the DC current flowing in the diode. It is normally specified at a small (i.e., 1 – 100 microamperes) current and can range from 500 ohms to megohms. Some ZBD’s are used without bias so RV is specified at zero bias. The video impedance can affect the pulse fidelity of a video detector since the RC time constant depends on RV and the bypass capacitor of the detector circuit.

vinyl

A form of plastic used as insulation, which has high dielectric strength and low water absorption.

viscosity

The measure of the resistance of a fluid to flow (either through a specific orifice or in a rotational viscometer). The absolute unit of viscosity measurement is the poise (or centipoise). Kinematic viscosity is expressed in strokes.

VLSI

Very Large Scale Integration – An IC that in complexity contains over 1000 gates or their equivalent.

Vmax

The highest voltage that can safely be dropped across a PolySwitch device in its tripped state under specified fault conditions.

VMG

Velocity Made Good. The rate of closure to a destination based upon your current speed and course.

VOD

Video On Demand

VoDSL

voice over digital subscriber line

voice-frequency

vf – Any frequency within that part of the audio-frequency range essential to speech transmission of commercial quality (ie 300 to 3400 Hz). Also referred to as telephone frequency.

VoIP

Voice over Internet protocol

volatile memory

A computer storage medium which is incapable of retaining information without continuous power dissipation.

volt

Abbreviated V. The unit of measurement of electromotive force. It is equivalent to the force required to produce a current of 1 ampere through a resistance of 1 ohm.

Volt Microsecond Constant

The product of the voltage applied across the winding and the time for the magnetizing current to reach 1.5 times the linear extrapolation of the current waveform. This constant is a measure of the entergy handling capability of a transformer or inductor. It is dependent upon the core area, core material (including the saturation flux density of the core), the number of turns of the winding and tile duty cycle of the applied pulse.

Voltage

Symbol E. The term most often used in place of electromotive force, potential, potential difference, or voltage drop to designate the electric pressure that exists between two points and that is capable of producing a current when a closed circuit is connected between the two points. Voltage is measured in volts, millivolts, microvolts, and kilovolts. The terms electromotive force, potential, potential difference, and voltage drop are all often called voltage.

Voltage Balance

For a multiple output converter, the percentage difference in voltage level of two outputs with opposite polarities and equal nominal values.

Voltage Breakdown

The voltage necessary to cause insulation failure.

Voltage Controlled Oscillator

An oscillator whose frequency is a function of an externally generated voltage control signal.

voltage drop

The voltage developed across a component or conductor by the flow of current through the resistance or impedance of that component or conductor. Often simply called voltage. Also called “drop.” The voltage across a resistor is usually called IR drop, while that in a conductor is usually called resistance drop.

Voltage Rating

The voltage that may be continuously applied to wire.

voltage regulator

A circuit capable of generating from a varying input voltage a constant output voltage to a varying load current.

Voltage Standing Wave Ratio)

VSWR – A measure of the uniformity of impedance along a transmission line, or the quality of the impedance match between a line and the source or load.

Voltage Tuned Filter

VTF – An electronically tunable, reactive circuit intended to pass or block portions of the electromagnetic spectrum, controlled by an externally generated voltage signal.

Volt-Ampere

VA – In an a.c. circuit, a measure of apparent power, given by: VA-EI, where E is the potential in volts; I is the curernt in amperes; and VA is apparent power in volt-amperes

Volt-Microsecond Constant

The product of the voltage applied across the winding and the time for the magnetizing current to reach 1.5 times the linear extrapolation of the current waveform. This constant is a measure of the energy handling capability of a transformer or inductor. It is dependent upon the core area, core material, number of turns, and the duty cycle of the applied pulse.

Volume Resistivity

The ability of a core to resist the flow of electrical current either through the bulk of the material or on its surface. The unit of the volume resistivity is Ohm-cm. Core volume resistivity becomes an issue in inductor designs where the leads/terminals come in contact with the core material. This type includes axial and radial inductors that have leads epoxied into the core. As for core materials, high permeability ferrites present the most concern as their volume resistivity is typically the lowest. Under certain conditions, a low resistive path can be realized between two inductor terminals if they are in contact with a low resistivity core. The inductor, under these conditions, will lose its higher impedance characteristics. Reciprocal of conductivity.

VPN

virtual private network

VSAT

Very small aperture terminal.

VSWR

Voltage Standing Wave Ratio – A measure of the uniformity of impedance along a transmission line, or the quality of the impedance match between a line and the source or load.

VTF

Voltage Tuned Filter – An electronically tunable, reactive circuit intended to pass or block portions of the electromagnetic spectrum, controlled by an externally generated voltage signal.

VTG

An NMEA message

vulcanization

A chemical reaction in which the physical properties of an elastomer are changed by reacting it with sulfur or other cross-linking agents.

VW-1

A rating determined by the Underwriters’ Laboratories’ (UL) optional Vertical Wire Flame Test—the most difficult flame test for tubing. Tubings with a VW-1 rating are highly flame-retardant. Formerly designated FR-1.