Malvino Chapter 24 MCQ With Answers

Malvino Chapter 24

Navy electricity and electronics training series (NEETS) (SuDoc D 207.217:EL 2/MOD.1-24/CD)

1. Voltage regulators normally use

a.  Negative feedback

b. Positive feedback

c.  No feedback

d. Phase limiting

a

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

b

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

b

4. A current-sensing resistor is usually

a. Zero

b. Small

c.  Large

d. Open

b

5. Simple current limiting produces too much heat in the

a. Zener diode    

b. Load resistor   

c. Pass transistor

d. Ambient air

c

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

a

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

c

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%

c

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% 

b   

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

a

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

c

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

b

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

b

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

b

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

a.  Positive

b. Negative

c.  Either positive or negative

d. Unregulated

a

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

a. 3 V

b. 4 V

c. 12 V

d. 40 V

c

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

b

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

d

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

c

20. A series regulator is an example of a

a.  Linear regulator

b. Switching regulator

c. Shunt regulator

d. Dc-to-dc converter

a

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

c

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

b

23. A power supply with low output impedance has low

a. Load regulation

b. Current limiting

c. Line regulation

d. Efficiency

a

24. A zener-diode regulator is a

a. Shunt regulator

b. Series regulator

c. Switching regulator

d. Zener follower

a

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

b

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

a

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

c

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

d

29. A switching regulator is considered

a. Quiet

b. Noisy

c. Inefficient

d. Linear

b

30. The zener follower is an example of a

a. Boost regulator

b. Shunt regulator

c. Buck regulator

d. Series regulator

d

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

c

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

a

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

a

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

c

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

a

36. The regulator with the highest efficiency is the

a. Shunt regulator

b. Series regulator

c. Switching regulator

d. Dc-to-dc converter

c

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

b

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

d