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
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