# Malvino: MCQ in Power Amplifiers

(Last Updated On: February 7, 2020)

This is the Multiple Choice Questions in Chapter 12: Power Amplifiers from the book Electronic Principles 7th Edition by Albert Malvino. 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.

### Topic Outline

• MCQs in Amplifier Terms
• MCQs in Two Load Lines
• MCQs in Class A Operation
• MCQs in Class B Operation
• MCQs in Class B Push-Pull Emitter Follower
• MCQs in Biasing Class B and Class AB Amplifiers
• MCQs in Class B and Class AB Drivers
• MCQs in Class C Operation
• MCQs in Class C Formulas
• MCQs in Transistor Power Rating

### Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. An emitter follower has a voltage gain that is

• a. Much less than one
• b. Approximately equal to one
• c. Greater than one
• d. Zero

2. The total ac emitter resistance of an emitter follower equals

• a. re’
• b. re
• c. re + re’
• d. RE

3. The input impedance of the base of an emitter follower is usually

• a. Low
• b. High
• c. Shorted to ground
• d. Open

4. The dc emitter current for class A emitter followers is

• a. The same as the ac emitter current
• b. VE divided by RE
• c. Vc divided by Rc
• d. The same as the load current

5. The ac base voltage of an emitter follower is across the

• a. Emitter diode
• b. DC emitter resistor
• d. Emitter diode and external ac emitter resistance

6. The output voltage of an emitter follower is across the

• a. Emitter diode
• b. DC collector resistor
• d. Emitter diode and external ac emitter resistance

7. If Beta = 200 and re = 150 ohm, the input impedance of the base is approximately

• a. 30 kohm
• b. 600 n
• c. 3 kohm
• d. 5 kohm

8. The input voltage to an emitter follower is usually

• a. Less than the generator voltage
• b. Equal to the generator voltage
• c. Greater than the generator voltage
• d. Equal to the supply voltage

9. The ac emitter current is closest to

• a. VG divided by re
• b. Vin divided by re’
• c. VG divided by re’
• d. Vin divided by re

10. The output voltage of an emitter follower is approximately

• a. 0
• b. VG
• c. Vin
• d. Vcc

11. The ac load line of an emitter follower is usually

• a. The same as the dc load line
• b. More horizontal than the dc load line
• c. Steeper than the dc load line
• d. Vertical

12. If the input voltage to an emitter follower is too large, the output voltage will be

• a. Smaller
• b. Larger
• c. Equal
• d. Clipped

13. If the Q point is at the middle of the dc load line, clipping will first occur on the

• a. Left voltage swing
• b. Upward current swing
• c. Positive half cycle of input
• d. Negative half cycle of input

14. If an emitter follower has VCEQ = 5 V, ICQ = 1 mA, and re = 1 kohm, the maximum peak-to-peak unclipped output is

• a. 1 V
• b. 2 V
• c. 5 V
• d. 10 V

15. If the load resistance of an emitter follower is very large, the external ac emitter resistance equals

• a. Generator resistance
• b. Impedance of the base
• c. DC emitter resistance
• d. DC collector resistance

16. If an emitter follower has re’ = 10 ohm and re = 90 ohm, the voltage gain is approximately

• a. 0
• b. 0.5
• c. 0.9
• d. 1

17. A square wave out of an emitter follower implies

• a. No clipping
• b. Clipping at saturation
• c. Clipping at cutoff
• d. Clipping on both peaks

18. A Darlington transistor has

• a. A very low input impedance
• b. Three transistors
• c. A very high current gain
• d. One VBE drop

19. The ac load line of the emitter follower is

• a. The same as the dc load line
• b. Different from the dc load line
• c. Horizontal
• d. Vertical

20. If the generator voltage is 5 mV in an emitter follower, the output voltage across the load is closest to

• a. 5 mV
• b. 150 mV
• c. 0.25 V
• d. 0.5 V

21. If the load resistor of Fig. 12-la in your textbook is shorted, which of the following are different from their normal values:

• a. Only ac voltages
• b. Only dc voltages
• c. Both dc and ac voltages
• d. Neither dc nor ac voltages

22. If R1 is open in an emitter follower, which of these is true?

• a. DC base voltage is Vcc
• b. DC collector voltage is zero
• c. Output voltage is normal
• d. DC base voltage is zero

23. Usually, the distortion in an emitter follower is

• a. Very low
• b. Very high
• c. Large
• d. Not acceptable

24. The distortion in an emitter follower is

• a. Seldom low
• b. Often high
• c. Always low
• d. High when clipping occurs

25. If a CE stage is direct coupled to an emitter follower, how many coupling capacitors are there between the two stages?

• a. 0
• b. 1
• c. 2
• d. 3

26. A Darlington transistor has a Beta of 8000. If RE = 1 kohm and RL = 100 ohm, the input impedance of the base is closest to

• a. 8 kohm
• b. 80 kohm
• c. 800 kohm
• d. 8 Mohm

27. The transistors of a class B push-pull emitter follower are biased at or near

• a. Cutoff
• b. The center of the dc load line
• c. Saturation
• d. The center of the ac load line

28. Thermal runaway is

• a. Good for transistors
• b. Always desirable
• c. Useful at times
• d. Usually destructive

29. The ac resistance of compensating diodes

• a. Must be included
• b. Is usually small enough to ignore
• c. Compensates for temperature changes
• d. Is very high

30. A small quiescent current is necessary with a class B push-pull amplifier to avoid

• a. Thermal runaway
• b. Destroying the compensating diodes
• c. Crossover distortion
• d. Excessive current drain

31. The zener current in a zener follower is

• a. Equal to the output current
• b. Smaller than the output current
• c. Larger than the output current
• d. Prone to thermal runaway

32. In the two-transistor voltage regulator, the output voltage

• a. Is regulated
• b. Has much smaller ripple than the input voltage
• c. Is larger than the zener voltage
• d. All of the above

33. For a class B push-pull emitter follower to work properly, the emitter diodes must

• a. Be able to control the quiescent current
• b. Have a power rating greater than the output power
• c. Have a voltage gain of I
• d. Match the compensating diodes

34. The maximum efficiency of a class B push-pull amplifier is

• a. 25 percent
• b. 50 percent
• c. 78.5 percent
• d. 100 percent

35. The ac emitter resistance of an emitter follower

• a. Equals the dc emitter resistance
• b. Is larger than the load resistance
• c. Has no effect on MPP
• d. Is usually less than the load resistance