How can FET be used as a variable resistor?

How can FET be used as a variable resistor?

FET is a device that is usually operated in the constant-current portion of its output characteristics. But if it is operated on the region prior to pinch-off (that is where VDS is small, say below 100 mV), it will behave as a voltage-variable resistor (WE).

In which region FET used as a voltage controlled resistor?

The saturation region , which includes each of the horizontally flat portions where the FET acts as a voltage-controlled current source and the other region that includes the sloped “curved portions” is the triode or ohmic region where the FET can operate as a voltage-controlled resistor.

Can a transistor be used as a variable resistor?

See the ohmic region in the graph can you see some linearity so yes, transistor can be used as a variable resistor and it’s resistance is varied by varying the voltage across gate and source VGS . More the voltage VGS more is the slope hence less is the resistance.

How a MOSFET can be used to amplify a time varying voltage?

BY appropriate choice of input resistance and output load you can make it into a voltage amplifier. With appropriate feedback you can make the gain factor of the amplifier more constant. Regardless of whether you only amplify current or voltage, there is also a power amplification gain figure.

Why FET is called voltage variable device?

JFET is a three-terminal device and since gate voltage controls the drain current, JFET is called a voltage-controlled device. JFET’s have only a depletion mode of operation. Thus drain current in JFET is controlled by changing the channel width.

How FET is voltage control device?

FET is a voltage-driven/controlled device, i.e. the output current is controlled by the electric field applied. The current through the two terminals is controlled by a voltage at the third terminal (gate). It has a high input impedance. So, a FET is a voltage-controlled current source.

Why is FET called current controlled resistor?

the electric field can be produced at the gate by applying some external voltage. So, in over all the current in fet is controlled by the voltage applied to gate which may increase or decrease the channel width inorder to control http://current.so so, this is the reason to call fet as voltage controlled device.

Can we use BJT as a resistor?

This is because collector and emitter cannot be exchanged without a drastic change in voltage-current characteristic. More than that, for Vce=0 the current Ic does not cross the origin for any finite control voltage Vbe. Hence, the BJT cannot be used as avoltage-controlled resistor.

Can BJT be used as a resistor?

BJT is a variable resistor. The resistance between Collector and Emitter is varied by the base current. So then BJT can be called as current controlled variable resistor.

How FET works as an amplifier?

A FET amplifier is an amplifier that uses one or more field-effect transistors (FETs). The most common type of FET amplifier is the MOSFET amplifier, which uses metal–oxide–semiconductor FETs (MOSFETs). The main advantage of a FET used for amplification is that it has very high input impedance and low output impedance.

Can MOSFETs be used as amplifier?

Any of the MOSFETs can be used as linear amplifiers. They must be biased so that majority current carriers flow from source to drain. The Gate-source capacitance is biased such that the transistor is operating midway between cutoff and saturation as with all transistor amplifiers.

What is differentdifferential amplifier?

Differential amplifier or diff-amp is a multi-transistor amplifier. It is the fundamental building block of analog circuit. It is virtually formed the differential amplifier of the input part of an operational amplifier. It is used to provide high voltage gain and high common mode rejection ratio.

When was the last time a differential amplifier was approved?

This version (06 Jun 2017 17:50) was approved by Doug Mercer. The Previously approved version (14 Apr 2015 23:31) is available. The differential amplifier is probably the most widely used circuit building block in analog integrated circuits, principally op amps.

What is the operation of the JFET amplifier 9-1?

9-1: The Common Source Amplifier JFET Amplifier Operation: AC Analysis The ac equivalent circuit can be drawn The amplifier circuit Ac equivalent circuit Ac equivalent circuit showing Vinand Vout Input resistance Very small Output resistance Rout= Rd with no RLÆ Rd= RD With load RLÆ Rd= RD//RL Voltage gain md gs ds in out v gR V V V V A = == 5

Can ævd= vdscan be calculated for an e-MOSFET amplifier?

ÆVD= VDScan be calculated The ac analysis is the same as for the JFET amplifier. 9-1: The Common Source Amplifier E-MOSFET Amplifier Operation: „A voltage divider common-source amplifier for n-channel E-MOSFET is shown. „The gate is biased with a positive voltage such that VGS> VGS(th)