Malvino Chapter 24

Chapter 24 

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 ofa 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 energyin 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 


Also try:

Malvino Chapter 1
Malvino Chapter 2
Malvino Chapter 3
Malvino Chapter 4
Malvino Chapter 5
Malvino Chapter 6
Malvino Chapter 7
Malvino Chapter 8
Malvino Chapter 9
Malvino Chapter 10
Malvino Chapter 11
Malvino Chapter 12
Malvino Chapter 13
Malvino Chapter 14
Malvino Chapter 15
Malvino Chapter 16
Malvino Chapter 17
Malvino Chapter 18
Malvino Chapter 19
Malvino Chapter 20
Malvino Chapter 21
Malvino Chapter 22
Malvino Chapter 23