Malvino: MCQ in Regulated Power Supplies

(Last Updated On: February 7, 2020)

This is the Multiple Choice Questions in Chapter 24: Regulated Power Supplies 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 Supply Characteristics
• MCQs in Shunt Regulators
• MCQs in Series Regulators
• MCQs in Monolithic Linear Regulators
• MCQs in Current Boosters
• MCQs in DC-to-DC Converters
• MCQs in Switching Regulators

Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. Voltage regulators normally use

• a. Negative feedback
• b. Positive feedback
• c. No feedback
• d. Phase limiting

2. During regulation, the power dissipation of the pass transistor equals the collector-emitter voltage times the

• a. Base current
• b. Load current
• c. Zener current
• d. Foldback current

3. Without current limiting, a shorted load will probably

• a. Produce zero load current
• b. Destroy diodes and transistors
• c. Have a load voltage equal to the zener voltage
• d. Have too little load current

4. A current-sensing resistor is usually

• a. Zero
• b. Small
• c. Large
• d. Open

5. Simple current limiting produces too much heat in the

• a. Zener diode
• b. Load resistor
• c. Pass transistor
• d. Ambient air

6. With foldback current limiting, the load voltage approaches zero, and the load current approaches

• a. A small value
• b. Infinity
• c. The zener current
• d. A destructive level

7. A capacitor may be needed in a discrete voltage regulator to prevent

• a. Negative feedback
• b. Excessive load current
• c. Oscillations
• d. Current sensing

8. If the output of a voltage regulator varies from 15 to 14.7 V between the minimum and maximum load current, the load regulation is

• a. 0
• b. 1%
• c. 2%
• d. 5%

9. If the output of a voltage regulator varies from 20 to 19.8 V when the line voltage varies over its specified range, the source regulation is

• a. 0
• b. 1%
• c. 2%
• d. 5%

10. The output impedance of a voltage regulator is

• a. Very small
• b. Very large
• c. Equal to the load voltage divided by the load current
• d. Equal to the input voltage divided by the output current

11. Compared to the ripple into a voltage regulator, the ripple out of a voltage regulator is

• a. Equal in value
• b. Much larger
• c. Much smaller
• d. Impossible to determine

12. A voltage regulator has a ripple rejection of -60 dB. If the input ripple is 1 V, the output ripple is

• a. -60 mV
• b. 1 mV
• c. 10 mV
• d. 1000 V

13. Thermal shutdown occurs in an IC regulator if

• a. Power dissipation is too high
• b. Internal temperature is too high
• c. Current through the device is too high
• d. All the above occur

14. If a linear three-terminal IC regulator is more than a few inches from the filter capacitor, you may get oscillations inside the IC unless you use

• a. Current limiting
• b. A bypass capacitor on the input pin
• c. A coupling capacitor on the output pin
• d. A regulated input voltage

15. The 78XX series of voltage regulators produces an output voltage that is

• a. Positive
• b. Negative
• c. Either positive or negative
• d. Unregulated

16. The 78XX-12 produces a regulated output voltage of

• a. 3 V
• b. 4 V
• c. 12 V
• d. 40 V

17. A current booster is a transistor in

• a. Series with the IC regulator
• b. Parallel with the IC regulator
• c. Either series or parallel
• d. Shunt with the load

18. To turn on a current booster, we can drive its base-emitter terminals with the voltage across

• a. A load resistor
• b. A zener impedance
• c. Another transistor
• d. A current-sensing resistor

19. A phase splitter produces two output voltages that are

• a. Equal in phase
• b. Unequal in amplitude
• c. Opposite in phase
• d. Very small

20. A series regulator is an example of a

• a. Linear regulator
• b. Switching regulator
• c. Shunt regulator
• d. Dc-to-dc converter

21. To get more output voltage from a buck switching regulator, you have to

• a. Decrease the duty cycle
• b. Decrease the input voltage
• c. Increase the duty cycle
• d. Increase the switching frequency

22. An increase of line voltage into a power supply usually produces

• a. A decrease in load resistance
• b. An increase in load voltage
• c. A decrease in efficiency
• d. Less power dissipation in the rectifier diodes

23. A power supply with low output impedance has low

• a. Load regulation
• b. Current limiting
• c. Line regulation
• d. Efficiency

24. A zener-diode regulator is a

• a. Shunt regulator
• b. Series regulator
• c. Switching regulator
• d. Zener follower

25. The input current to a shunt regulator is

• a. Variable
• b. Constant
• c. Equal to load current
• d. Used to store energy in a magnetic field

26. An advantage of shunt regulation is

• a. Built-in short-circuit protection
• b. Low power dissipation in the pass transistor
• c. High efficiency
• d. Little wasted power

27. The efficiency of a voltage regulator is high when

• a. Input power is low
• b. Output power is high
• c. Little power is wasted
• d. Input power is high

28. A shunt regulator is inefficient because

• a. It wastes power
• b. It uses a series resistor and a shunt transistor
• c. The ratio of output to input power is low
• d. All of the above

29. A switching regulator is considered

• a. Quiet
• b. Noisy
• c. Inefficient
• d. Linear

30. The zener follower is an example of a

• a. Boost regulator
• b. Shunt regulator
• c. Buck regulator
• d. Series regulator

31. A series regulator is more efficient than a shunt regulator because

• a. It has a series resistor
• b. It can boost the voltage
• c. The pass transistor replaces the series resistor
• d. It switches the pass transistor on and off

32. The efficiency of a linear regulator is high when the

• a. Headroom voltage is low
• b. Pass transistor has a high power dissipation
• c. Zener voltage is low
• d. Output voltage is low

33. If the load is shorted, the pass transistor has the least power dissipation when the regulator has

• a. Foldback limiting
• b. Low efficiency
• c. Buck topology
• d. A high zener voltage

34. The dropout voltage of standard monolithic linear regulators is closest to

• a. 0.3 V
• b. 0.7 V
• c. 2 V
• d. 3.1 V

35. In a buck regulator, the output voltage is filtered with a

• a. Choke-input filter
• b. Capacitor-input filter
• c. Diode
• d. Voltage divider

36. The regulator with the highest efficiency is the

• a. Shunt regulator
• b. Series regulator
• c. Switching regulator
• d. Dc-to-dc converter

37. In a boost regulator, the output voltage is filtered with a

• a. Choke-input filter
• b. Capacitor-input filter
• c. Diode
• d. Voltage divider

38. The buck-boost regulator is also

• a. A step-down regulator
• b. A step-up regulator
• c. An inverting regulator
• d. All of the above

Check your work.

Complete List of MCQ in Electronic Principles by Albert Malvino