# Floyd: MCQ in FET Amplifiers and Switching Circuits

(Last Updated On: August 23, 2019)

This is the Multiple Choice Questions in FET Amplifiers and Switching Circuits from the book Electronic Devices – Electron Flow Version and Conventional Current Version 8th Edition by Thomas L. Floyd. If you are looking for a reviewer in Electronics Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

#### Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. A common-drain amplifier is similar in configuration to which BJT amplifier?

A. common-emitter

B. common-collector

C. common-base

D. common-gate

Solution:

2. A common-source amplifier is similar in configuration to which BJT amplifier?

A. common-base

B. common-collector

C. common-emitter

D. emitter-follower

Solution:

3. A common-gate amplifier is similar in configuration to which BJT amplifier?

A. common-emitter

B. common-collector

C. common-base

D. emitter-follower

Solution:

4. In a common-source amplifier, the purpose of the bypass capacitor, C2, is to

A. keep the source effectively at ac ground.

B. provide a dc path to ground.

C. provide coupling to the input.

D. provide coupling to the load.

Solution:

5. Which FET amplifier(s) has (have) a phase inversion between input and output signals?

A. common-gate

B. common-drain

C. common-source

D. all of the above

Solution:

6. Input resistance of a common-drain amplifier is

A. RG || RIN(gate).

B. RG + RIN(gate).

C. RG.

D. RIN(gate).

Solution:

7. Refer to Figure 9-1. For midpoint biasing, ID would be

Figure 9-1

A. 10 mA.

B. 7.5 mA.

C. 5 mA.

D. 2.5 mA.

Solution:

8. Refer to Figure 9-1. Find the value of VD.

A. 20 V

B. 11 V

C. 10 V

D. 9 V

Solution:

9. Refer to Figure 9-1. If VGS = –6 V, calculate the value of RS that will provide this value.

A. 2.2 kΩ

B. 1.2 kΩ

C. 600 kΩ

D. 100 kΩ

Solution:

10. Refer to Figure 9-1. The voltage gain is

A. 1.2.

B. 2.4.

C. 4.4.

D. 8.8.

Solution:

11. Refer to Figure 9-1. If Vin = 20 mV p-p what is the output voltage?

A. 176 mV p-p

B. 88 mV p-p

C. 48 mV p-p

D. 24 mV p-p

Solution:

12. Refer to Figure 9-1. If Vin = 1 V p-p, the output voltage Vout would be

A. undistorted.

B. clipped on the negative peaks.

C. clipped on the positive peaks.

D. 0 V p-p.

Solution:

13. Refer to Figure 9-2. If ID = 4 mA, IDSS = 16 mA, and VGS(off) = –8 V, find VDS.

Figure 9-2

A. 19.2 V

B. –6 V

C. 10.8 V

D. 30 V

Solution:

14. Refer to Figure 9-2. If ID = 4 mA, find the value of VGS.

A. 10.8 V

B. 6 V

C. –0.7 V

D. –6 V

Solution:

15. Refer to Figure 9-2. If gm = 4000 mS and a signal of 75 mV rms is applied to the gate, calculate the p-p output voltage.

A. 990 mV

B. 1.13 V p-p

C. 2.8 V p-p

D. 990 V p-p

Solution:

16. Refer to Figure 9-2. The approximate value of Rin is

A. 100 MΩ.

B. 1.5 kΩ.

C. 3.3 kΩ.

D. 48 MΩ.

Solution:

17. Refer to Figure 9-3. If C4 opened, the signal voltage at the drain of Q1 would

Figure 9-3

A. increase.

B. decrease.

C. remain the same.

D. distort.

Solution:

18. Refer to Figure 9-3. If R7 were to decrease in value, Vout would

A. increase.

B. decrease.

C. remain the same.

D. distort.

Solution:

19. Refer to Figure 9-3. If C2 shorted, Vout would

A. increase.

B. decrease.

C. remain the same.

D. distort.

Solution:

20.Refer to Figure 9-3. If Vin was increased in amplitude a little, the signal voltage at the source of Q2 would

A. increase.

B. decrease.

C. remain the same.

D. distort.

Solution:

21. Refer to Figure 9-3. If R6 opened, the signal at the drain of Q1 would

A. increase.

B. decrease.

C. remain the same.

D. distort.

Solution:

22. A JFET cascade amplifier employs

A. 2 common-gate amplifiers.

B. 2 common-source amplifiers.

C. 1 common-gate and 1 common-source amplifier.

D. 1 common-gate and 1 common-drain amplifier.

Solution:

23. The theoretical efficiency of a class D amplifier is

A. 75%.

B. 85%.

C. 90%.

D. 100%.

Solution:

24. The input resistance at the gate of a FET is extremely

A. high.

B. low.

C. 0

D. infinite

Solution:

25. There is a _____° phase inversion between gate and source in a source follower.

A. 0

B. 90

C. 180

D. none of the above

Solution:

26. What is the input resistance (Rin(source)) of a common-gate amplifier?

A. Rs

B. (1/gm)||Rs

C. 1/gm

D. none of the above

Solution:

27. Which type of FETs can operate with a gate-to-source Q-point value of 0 V?

A. JFET

B. E-MOSFET

C. D-MOSFET

D. none of the above

Solution:

28. What common factor determines the voltage gain and input resistance of a common-gate amplifier?

A. RD

B. RL

C. gm

D. none of the above

Solution:

29. The class D amplifier uses what type of transistors?

A. JFETs

B. BJTs

C. MOSFETs

D. any of the above

Solution:

30. Class D amplifiers differ from all other classes of amplifiers because

A. the output transistors are operated as switches.

B. of their very low input capacitance.

C. of their high-frequency response capabilities.

D. they employ dual MOSFETs.

Solution:

31. E-MOSFETs are generally used in switching applications because

A. of their very low input capacitance.

B. of their threshold characteristic (VGS(th)).

C. of their high-frequency response capabilities.

D. of their power handling.

Solution:

32. What limits the signal amplitude in an analog MOSFET switch?

A. the switch input capacitance

B. VGS(th)

C. the switch’s power handling

D. VDS

Solution:

33. MOSFET digital switching is used to produce which digital gates?

A. inverters

B. NOR gates

C. NAND gates

D. all of the above

Solution:

34. CMOS digital switches use

A. n-channel and p-channel D-MOSFETs in series.

B. n-channel and p-channel D-MOSFETs in parallel.

C. n-channel and p-channel E-MOSFETs in series.

D. n-channel and p-channel E-MOSFETs in parallel.

Solution:

35. MOSFETs make better power switches than BJTs because they have

A. lower turn-off times.

B. lower on-state resistance.

C. a positive temperature coefficient.

D. all of the above

Solution:

#### TRUE/FALSE:

1. The voltage gain of a common-source amplifier is found by the product of gm and Rd.

A. True

B. False

Solution:

2. There is no phase inversion between the gate and the drain voltages.

A. True

B. False

Solution:

3. There is a 180º phase inversion between the gate and source voltages.

A. True

B. False

Solution:

4. A load resistance connected to the output of an amplifier reduces the voltage gain.

A. True

B. False

Solution:

5. Bypassing a source resistor reduces the voltage gain.

A. True

B. False

Solution:

6. Generally, higher voltage gains can be achieved with bipolar amplifiers than with FET amplifiers.

A. True

B False

Solution:

7. The common-drain amplifier is also called a source-follower.

A. True

B. False

Solution:

8. The common-gate configuration has extremely high input resistance.

A. True

B. False

Solution:

9. The common-source configuration has extremely high input resistance.

A. True

B. False

Solution:

10. The common-drain configuration has extremely high input resistance.

A. True

B. False

Solution:

11. In a class D amplifier, the output transistors are operated in a nonlinear mode.

A. True

B. False

Solution:

12. Class D amplifier efficiencies can reach practical levels of more than 90%.

A. True

B. False

Solution:

13. In a class D amplifier, the low-pass filter comes directly after the pulse-width modulator.

A. True

B. False

Solution:

14. In an analog MOSFET switch, the input is applied to the gate and the output is taken from the source.

A. True

B. False

Solution:

15. Digital MOSFET switches are used in the sample-and-hold circuit of an analog-to-digital converter.

A. True

B. False