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.

Can FET be used as a 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.

In which region FET can be used as a voltage-variable resistor?

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 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.

What are the FET region of operation?

Saturation region: The FET becomes a good conductor and ID is controlled by the Gate-Source voltage, (VGS) while the Drain-Source voltage, (VDS) has little or no effect. Current ID flowing from drain to source is maximum thus it is referred as saturation region.

JFET as Voltage-Controlled Resistor

What is ohmic region in FET?

The ohmic region of JFET is a region at which drain current shows linear behavior for variation in the drain-source voltage. This behavior is like to the ohms law so called ohmic region. The value of ID depend on the drain-source voltage VDS.

What are the operating regions of a JFET?

Mainly the JFET operates in ohmic, saturation, cut-off and break-down regions.

How FET can be used as voltage controlled resister?

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.

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.

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.

Why FET is called voltage control resistor?

It is due to the fact that in this region drain-to-source resistance R_DS can be controlled by varying the bias voltage V_GS. In such applications the FET is also referred to as a voltage-variable resistor or volatile dependent resistor. It finds applications in many areas where this property is useful.

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.

When used as switch transistor is operate in region?

If a positive signal applied at the input terminal then it acts like a closed switch. When the transistor operating as switch, in the cut off region the current through the transistor is zero and voltage across it is maximum, and in the saturation region the transistor current is maximum and voltage across is zero.

Which of the following statement is true about a FET?

Which of the following statement is true about FET? Explanation: Because of the Sio2 insulator, doped between drain and source at the top, the resistance offered by this is very high. The insulator will stop the flow of electron from one part to another which acts as an open circuit.

How can we use FET as VVR?

The FET is useful as a voltage variable resistor (VVR) or Voltage Dependent resistor. In JFET the drain source conductance gd=IdVDS for small values of VDS which may be expressed as gd=gd0[1−(VGSVp)1/2] where gd0 is the value of drain conductance when the bias voltage VGS is zero.

How can JFET be biased in the ohmic region?

The ohmic region is the portion of the FET characteristic curves (shown in figure) in which Ohm's law can be applied. When properly biased in the ohmic region, a JFET exhibits the properties of a variable resistance, where the value of resistance between drain and source (RDS) is controlled by VGS.

In which region MOSFET acts as switch?

In order to operate a MOSFET as a switch, it must be operated in cut-off and linear (or triode) region.

What is the condition for saturation region?

The transistor operates in saturation region when both the emitter and collector junctions are forward biased. As it is understood that, in the saturation region the transistor tends to behave as a closed switch, we can say that, IC=IE. Where IC = collector current and IE = emitter current.

What is the condition for non saturated region *?

The condition for non saturated region is Vds lesser Vgs – Vt. In non saturation region MOSFET acts as voltage source. Varying Vds will provide significant change in drain current.

Is FET voltage controlled current source?

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.

Is JFET and FET same?

FET is categorized into JFET (Junction Field Effect Transistor) and MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Both are mainly used in integrated circuits and are quite similar in operating principles, but they have a slight different composition.

What is the main reason why FETs are commonly used in integrated circuits?

FET uses the voltage applied to its input terminal (called the Gate), to control the current flowing from the source to drain, making the Field Effect Transistor a “Voltage” operated device. FETs are extensively used in Integrated Circuits (ICs) due to their compact size and significantly lower power consumption.

Which region is ohmic region?

The third region is known as the ohmic region, or triode region. It occurs in the area where VDS is less than the pinch-off voltage, VP. In this area, the device behaves more like a resistor than like a current source.