Q. Why FET is called a voltage-controlled device? Why its input resistance is high?

In the case of a FET the output current ID is a function of the voltage VGS applied to the input circuit. Hence FET is known as a voltage controlled device. The equation that governs the working of a FET is called Shockley's equation given by,

I_D = I_DSS[1 - (V_GS/V_P) ^₂

where, ID is the drain current

I_DSS is the maximum saturation current

V_GS is the voltage applied between gate and source

V_P is the pinch-off voltage

A FET requires virtually no input current and hence IG is always made zero. This gives an extremely high input resistance to FET. The range of its input impedance is at a level of 1 to several 100MWs.

Posted Date: 6/11/2013 6:07:08 AM | Location : United States

Ask an Expert

Related Discussions:- Why fet is called a voltage-controlled device, Assignment Help, Ask Question on Why fet is called a voltage-controlled device, Get Answer, Expert's Help, Why fet is called a voltage-controlled device Discussions

Write discussion on Why fet is called a voltage-controlled device
Your posts are moderated

Write your message here..

Related Questions

Interpretation and analysis using remote sensing, Q. Interpretation and ana... Q. Interpretation and analysis using remote sensing? Interpretation and analysis using remote sensing Various characteristics of a river can be understood by studying its planf

Illustrate power semiconductor devices, Q. Illustrate Power Semiconductor D... Q. Illustrate Power Semiconductor Devices? Since the advent of the first thyristor or silicon-controlled rectifier (SCR) in 1957, tremendous advances have been made in power se

Excitation, excitation in an ac generator excitation in an ac generator

Sonic harassment, Sir I would like to find a sensor that can detect beams ... Sir I would like to find a sensor that can detect beams from the phasor painfield generator and the sonic devasator (devices of this nature). These sonic devices emit a high pres

Illustrate differential phase-shift keying, Q. Illustrate Differential phas... Q. Illustrate Differential phase-shift keying? In order to eliminate the need of a local carrier, DPSK has been developed in which the receiver uses the received signal to act

Determine the speed at which the machine runs as a motor, A 100-kW, dc shun... A 100-kW, dc shunt generator, connected to a 220-V main, is belt-driven at 300 r/min, when the belt suddenly breaks and the machine continues to run as a motor, taking 10 kW from t

Determine the function of time for the clock, Q. Determine the function of ... Q. Determine the function of time for the clock? Given the block diagram for a 4-bit shift-left register shown in Figure (a), draw the output (Q 0 , Q 1 , Q 2 , Q 3 , and data

Balanced budget laws, Balanced Budget Laws: Laws (usually passed by right-w... Balanced Budget Laws: Laws (usually passed by right-wing governments) that require governments to run balanced budgets regardless of state of the overall economy. These lawshave th

Microprocessor, Memory map of tpa in a personal computer and explain such o... Memory map of tpa in a personal computer and explain such of the areas in brief

Determine the parameters of the equivalent circuit, The no-load and blocked... The no-load and blocked-rotor tests on a three phase, wye-connected induction motor yield the following results: • No-load test: line-to-line voltage 400 V, input power 1770 W,