Can FET be used as a 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.

Is FET can be used as variable resistor?

Variable resistors are widely used in electric circuits to adjust the value of current or voltage, since the resistance of variable resistors can be set to a certain value. Variable resistors allow you to adjust the value of voltage by changing the resistance and keeping current constant .

Can FET be used as a resistor if yes in which region is this operation possible?

In its simplest form, the JFET can be used as a voltage-controlled resistor where a small gate voltage controls the conduction of its channel.

How can a FET be used as a variable resistor in a circuit?

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.

How FET can be used as voltage-controlled resistor?

When the drain current is reduced to a point where the FET is no longer conductive, the maximum resistance is reached. The voltage at this point is referred to as the pinchoff or cutoff voltage and is symbolized by VGS = VGS(off). Thus the device functions as a voltage- controlled resistor.

JFET as Voltage-Controlled Resistor

In which region JFET acts as a resistor?

In the triode region, the JFET acts like a resistor, however, in the saturation region it behaves like a constant-current source. The point that separates the triode region and the saturation region is roughly the point where V_DS is equal to V_GS on each of the IV curves.

In which region FET used as a voltage controlled resistor?

Note: The triode or ohmic region in an FET is sometimes known as the linear region. The FET operating as a voltage-controlled resistor (VCR) works in this region.

How FET can be used 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.

Where is FET used?

They are used in mixer circuits of TV and FM receivers due to low intermodulation distortions. Moreover FETs are also used as voltage-variable resistors in OP-AMPS, tone control circuits and JFET voltmeter design.

Why FET is used as constant-current source?

The combination of low associated operating voltage and high output impedance makes the FET attractive as a constant-current source. An adjustable-current source (Fig- ure 1) may be built with a FET, a variable resistor, and a small battery.

Which region FET can be used as amplifier?

A field-effect transistor works as a voltage variable resistor in the ohmic region. It works as an amplifier in the saturation region.

In which region FET acts as an amplifier?

The input signal, (Vin) of the common source JFET amplifier is applied between the Gate terminal and the zero volts rail, (0v). With a constant value of gate voltage Vg applied the JFET operates within its “Ohmic region” acting like a linear resistive device. The drain circuit contains the load resistor, Rd.

Can a variable resistor be used as a switch?

There is a switch method in which variable resistors with the annular cross-section are used for controlling the equipment. The track made in a straight path is called a slider.

Is a rheostat a resistor?

rheostat, adjustable resistor used in applications that require the adjustment of current or the varying of resistance in an electric circuit. The rheostat can adjust generator characteristics, dim lights, and start or control the speed of motors.

Which of the following device is used as a variable resistor?

Rheostat is the device in a circuit which is used to provide variable resistance ....

What is FET and its applications?

Field effects transistors (FETs) are used in mixer circuits to control low inter modulation distortions. FETs are used in low frequency amplifiers due to its small coupling capacitors. It is a voltage controlled device due to this it is used in operational amplifier as voltage variable resistors.

What are the advantages of FET?

Why FET is superior to BJT as amplifier?

FETs offer greater input impedance than BJTs. This means that they practically draw no current and therefore do not load down the power circuit that's feeding it. BJTs offer greater gain at the output than FETs. The gain (or transconductance) of FETs are smaller than for BJTs.

Why FET is called field-effect?

The concept of the field effect transistor is based around the concept that charge on a nearby object can attract charges within a semiconductor channel. It essentially operates using an electric field effect - hence the name.

What is the impedance of FET?

The input impedance of an amplifier can be tens of ohms, (Ohms Ω) to a few thousand ohms, (kilo-ohms kΩ) for bipolar based transistor circuits up to millions of ohms, (Mega-ohms MΩ) for FET based transistor circuits.

What are the advantages of FET over BJT?

FETs are more temperature stable than BJTs. FETs are generally easier to fabricate than BJTs. Greater numbers of devices can be fabricated on a single chip (i.e., increased packing density is possible). FETs react like voltage-controlled variable resistors for small values of drain-to-source voltage.

At what condition a JFET can be used as a voltage controlled resistor Why is the VI characteristics linear in that region?

Ohmic Region – When V_GS = 0 the depletion layer of the channel is very small and the JFET acts like a voltage controlled resistor.