FET Switches: Enhancement and Depletion Modes, Switching Characteristics, Digital Circuit Applications

Question 1

Which of the following accurately describes an enhancement-mode FET?

Accepted Answer

It does not conduct when no gate voltage is applied and requires a positive gate voltage to turn on.

Answer

It conducts when no gate voltage is applied and requires a negative gate voltage to turn off.

Answer

It always conducts and cannot be turned off.

Answer

It never conducts and cannot be turned on.

Question 2

What is the primary distinction between JFETs and MOSFETs?

Accepted Answer

JFETs use a junction to control current flow, whereas MOSFETs employ an insulated gate.

Answer

MOSFETs use a junction to control current flow, whereas JFETs employ an insulated gate.

Answer

JFETs are minority carrier devices, whereas MOSFETs are majority carrier devices.

Answer

MOSFETs are minority carrier devices, whereas JFETs are majority carrier devices.

Question 3

In an FET-based logic gate, what is the purpose of a pull-up resistor?

Accepted Answer

To provide a current path when the FET is off

Answer

To prevent accidental FET turn-on

Answer

To limit FET current flow

Answer

To enhance output voltage swing

Question 4

Define a depletion-mode FET.

Accepted Answer

An FET that conducts without a gate voltage and requires a positive gate voltage to turn off

Answer

An FET that does not conduct without a gate voltage and requires a negative gate voltage to turn on

Answer

An FET that always conducts and cannot be turned off

Answer

An FET that never conducts and cannot be turned on

Question 5

What is the function of the source terminal in an FET?

Accepted Answer

To provide a low-resistance path for electrons to enter the channel

Answer

To provide a high-resistance path for electrons to exit the channel

Answer

To regulate the gate voltage

Answer

To control the current flow through the channel

Question 6

What is the impact of increasing the gate-source voltage in an enhancement-mode FET?

Accepted Answer

Increases drain current

Answer

Decreases drain current

Answer

No effect on drain current

Answer

Reverses drain current direction

Question 7

What is a key characteristic of FET switches?

Accepted Answer

High input impedance

Answer

Always in the ON state

Answer

Low switching speed

Question 8

Which of the following is not a type of Field-Effect Transistor (FET)?

Accepted Answer

BJT

Answer

JFET

Answer

MOSFET

Answer

MESFET

Question 9

Which of the following is a key characteristic of enhancement-mode FETs?

Accepted Answer

Current flows when the gate-source voltage is positive.

Answer

Current flows when the gate-source voltage is negative.

Answer

Current flows when the gate-source voltage is zero.

Answer

Current flows when the gate-source voltage is below the pinch-off voltage.

Question 10

In depletion-mode FETs, the channel is initially:

Accepted Answer

Depleted

Answer

Accumulated

Question 11

Which of the following is NOT a switching characteristic of FETs?

Accepted Answer

High linearity

Answer

High switching speed

Answer

Low on-resistance

Answer

Low power dissipation

Question 12

The drain current in a FET is controlled primarily by:

Accepted Answer

Gate-source voltage

Answer

Drain-source voltage

Answer

Channel length

Answer

Channel width

Question 13

In a JFET, the gate-source junction is:

Accepted Answer

Reversed-biased

Answer

Forward-biased

Question 14

An n-channel enhancement-mode FET conducts current when:

Accepted Answer

A positive gate-source voltage is applied.

Answer

A negative gate-source voltage is applied.

Answer

No gate-source voltage is applied.

Answer

It is in the depletion region.

Question 15

Which characteristic accurately describes an N-channel enhancement mode Field-Effect Transistor (FET)?

Accepted Answer

Conducts electricity when the gate-to-source voltage is positive

Answer

Has a negative threshold voltage

Answer

Carries current even without a gate voltage

Answer

Is a depletion-mode transistor

Question 16

What is the primary purpose of a depletion mode FET?

Accepted Answer

Function as switches

Answer

Control voltage levels

Answer

Amplify signals

Answer

Stabilize current flow

Question 17

Which parameter is NOT used to characterize FET switches?

Accepted Answer

Voltage gain

Answer

Threshold voltage

Answer

Transconductance

Answer

Maximum drain current

Question 18

A Field-Effect Transistor (FET) in enhancement mode conducts when:

Accepted Answer

The gate-source voltage is positive

Answer

The gate-source voltage is zero

Answer

The gate-source voltage is negative

Answer

There is no gate voltage

Question 19

What is a key advantage of using MOSFETs in digital circuits?

Accepted Answer

High speed and low power consumption

Answer

Ability to handle high currents

Answer

Resistance to voltage spikes

Answer

Low input impedance

Question 20

In a JFET depletion mode, a negative gate-source voltage is required to:

Accepted Answer

Turn off the transistor

Answer

Conduct current

Answer

Increase drain current

Answer

Reverse the direction of drain current

Question 21

In a FET switching circuit, the input that controls the output is the:

Accepted Answer

Gate-source voltage

Answer

Drain current

Answer

Switching time

Answer

Gate threshold voltage

Question 22

When a negative voltage is applied to the gate of an N-channel JFET, the:

Accepted Answer

Drain current decreases

Answer

Drain current increases

Answer

Direction of drain current reverses

Answer

FET turns off completely

Question 23

A common application of FETs in digital circuits is:

Accepted Answer

Logic gates

Answer

Amplifiers

Answer

Voltage regulators

Answer

Sensors

Question 24

The ability of a FET to resist changes in drain current due to temperature variations is called its:

Accepted Answer

Thermal stability

Answer

Transconductance

Answer

Gate capacitance

Answer

Breakdown voltage

Question 25

In a FET, the depletion layer:

Accepted Answer

Controls the flow of carriers

Answer

Protects the gate from damage

Answer

Reduces noise

Answer

Increases power dissipation

Question 26

JFETs are distinguished from other FETs by the presence of which terminal?

Accepted Answer

Floating body

Answer

Floating gate

Answer

Floating source

Answer

Floating drain

Question 27

Which mode of operation for FETs results in a normally-on state?

Accepted Answer

Depletion mode

Answer

Enhancement mode

Answer

Cutoff mode

Answer

Ohmic region

Question 28

FETs are commonly used in a wide range of electronic applications. Which of the following is NOT a typical application for FET switches?

Accepted Answer

Memory storage

Answer

Digital logic gates

Answer

Analog amplifiers

Answer

Power control

Question 29

What is the main advantage of using FETs in digital circuits compared to other types of transistors?

Accepted Answer

Higher input impedance

Answer

Lower power consumption

Answer

Faster switching speed

Answer

Lower cost

Question 30

A major disadvantage of using FETs in power control applications is their:

Accepted Answer

High on-resistance

Answer

Low switching speed

Answer

High gate capacitance

Answer

Low current handling capability

Question 31

In enhancement mode MOSFETs, the relationship between threshold voltage (Vth) and gate-source voltage (Vgs) is:

Accepted Answer

Vgs > Vth

Answer

Vgs < Vth

Answer

Vgs = Vth

Answer

Vgs > 2Vth

Question 32

In a digital circuit, the primary role of a FET is:

Accepted Answer

Signal switching

Answer

Signal amplification

Answer

Signal filtering

Answer

Signal oscillation

Question 33

When compared to JFETs, the main advantage of MOSFETs lies in their:

Accepted Answer

Higher input impedance

Answer

Lower power consumption

Answer

Faster switching capability

Answer

Lower noise generation

Question 34

In a JFET, increasing the gate-source voltage results in:

Accepted Answer

Increased drain current

Answer

Decreased drain current

Answer

Increased gate current

Answer

Decreased gate current

Question 35

In a FET circuit, the purpose of a pull-up resistor is to:

Accepted Answer

Provide a current path when the FET is off

Answer

Limit the flow of gate current

Answer

Enhance the rise time of the output signal

Answer

Reduce the overall power consumption

Question 36

Depletion-mode FETs are commonly employed in:

Accepted Answer

Switching applications

Answer

Amplifiers

Answer

Voltage regulation circuits

Answer

Oscillators

Question 37

The primary advantage of using FETs in power electronics systems stems from their:

Accepted Answer

Ability to handle high currents

Answer

Low power dissipation

Answer

Rapid switching speeds

Answer

Low noise generation

Question 38

To ensure an n-channel JFET operates in the ohmic region, which biasing method should be used?

Accepted Answer

Zero-bias

Answer

Gate-to-source voltage

Answer

Drain-to-source voltage

Question 39

Which of the following is NOT a mode of operation for a Field-Effect Transistor (FET)?

Accepted Answer

Triode mode

Answer

Depletion mode

Answer

Enhancement mode

Answer

Cutoff mode

Question 40

An N-channel FET is in enhancement mode. What is the threshold voltage (Vth)?

Accepted Answer

Positive voltage

Answer

Dependent on gate material

Answer

Negative voltage

Answer

Zero voltage

Question 41

In a common-source amplifier configuration using an enhancement mode FET, what is the purpose of the source resistor (Rs)?

Accepted Answer

To provide bias current

Answer

To increase bandwidth

Answer

To reduce gain

Answer

To prevent oscillations

Question 42

What is the role of the gate-source capacitance (Cgs) in a FET switch?

Accepted Answer

Determines switching speed

Answer

Provides bias current

Answer

Reduces power consumption

Answer

Controls output voltage

Question 43

FET switches offer numerous advantages, but which of the following is true about their performance?

Accepted Answer

They can be used in both digital and analog applications.

Answer

They are always faster than BJTs.

Answer

They require high gate drive currents.

Question 44

In a totem-pole output stage using FETs, what is the purpose of the pull-up resistor?

Accepted Answer

To provide a high output voltage when both FETs are off.

Answer

To prevent oscillations

Answer

To reduce power consumption

Question 45

Which of the following is a limitation of using FETs in high-frequency applications?

Accepted Answer

Gate-source capacitance

Answer

Low input impedance

Answer

High threshold voltage

Answer

Poor thermal stability

Question 46

In a logic circuit using FET switches, what is the function of a Schmitt trigger?

Accepted Answer

To eliminate noise and improve signal integrity.

Answer

To reduce power consumption

Answer

To provide level shifting

Answer

To increase switching speed

Question 47

What is the purpose of the gate terminal in an FET switch?

Accepted Answer

Controls the flow of current between the source and drain terminals.

Answer

Provides a voltage reference for the FET.

Answer

Amplifies the input signal.

Question 48

Which type of FET requires a positive gate voltage to turn on (Enhancement Mode)?

Accepted Answer

Enhancement-mode MOSFET (NMOS or PMOS)

Answer

Depletion-mode MOSFET

Answer

JFET

Question 49

In a depletion-mode MOSFET, what is the effect of applying a negative gate voltage?

Accepted Answer

It reduces the channel conductivity.

Answer

It has no effect on the channel conductivity.

Answer

It increases the channel conductivity.

Question 50

What is the main application of FET switches in digital circuits?

Accepted Answer

Logic gates and multiplexers.

Answer

Voltage regulators and power supplies.

Answer

Filters and signal conditioning.

Answer

Amplifiers and oscillators.

Question 51

Which parameter represents the minimum gate-to-source voltage required to turn on an enhancement-mode MOSFET?

Accepted Answer

Threshold voltage (Vgs(th))

Answer

Drain-to-source voltage (Vds)

Answer

On-resistance (Ron)

Question 52

A FET switch is used to control a 100mA load current. The on-resistance of the FET is 10 ohms. What is the voltage drop across the switch when it is turned ON?

Accepted Answer

1V

Answer

10V

Answer

100V

Answer

0.1V

Question 53

What is the main advantage of using a CMOS inverter compared to a bipolar inverter?

Accepted Answer

Lower power consumption.

Answer

Higher speed.

Answer

Higher current handling capacity.

Answer

Simpler to design.