boylestad electronics multiple choice q&a chapter (12)

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Site Title: Electronic Devices and Circuit Theory Book Author: Boylestad

Location on Site: Chapter 12 > Multiple Choice Date/Time

Submitted:

October 12, 2012 at 12:44 AM (UTC/GMT)

Summary of Results

17% Correct of 35 Scored item s: 6 Correct: 17%

29 Incorrect: 83%

More inform ation about scoring

1.

Which of the following is (are) power amplifiers?

Your Answer:Class A

Correct Answer: All of the above

2.

By how much does the output signal vary for a class AB power amplifier? Your Answer:360º

Correct Answer: Between 180º and 360º

3.

Which type of power amplifier is biased for operation at less than 180º of the cycle? Your Answer:Class A

Correct Answer: Class C

4.

Which type of amplifier uses pulse (digital) signals in its operation? Your Answer:Class C

Correct Answer: Class D

5.

Which of the power amplifiers has the lowest overall efficiency? Your Answer: Class A

6.

Which of the following describe(s) a power amplifier? Your Answer:It can handle large power.

7.

_____ amplifiers primarily provide sufficient power to an output load to drive a speaker from a few watts to tens of watts.

Your Answer:Small-signal

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8.

The main features of a large-signal amplifier is the circuit's ______. Your Answer:impedance matching to the output device

9.

This is an example of the output swing for a class _____ amplifier.

Your Answer:AB

Correct Answer: A

10.

This is an example of the output swing for a class _____ amplifier.

Your Answer:A

Correct Answer: B

11.

Class AB operation is _____ operation.

Your Answer:similar to class B

Correct Answer: None of the above

12.

Which operation class is generally used in radio or communications? Your Answer:B

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13.

Your Answer:A, B, AB, D

Correct Answer: A, AB, B, D

14.

What is the maximum efficiency of a class A circuit with a direct or series-fed load connection? Your Answer:78.5%

Correct Answer: 25%

15.

What is the ratio of the secondary voltage to the primary voltage with the turn ratio in the windings?

Your Answer:_(N₁_/N₂₎2 Correct Answer: N₂/N₁

16.

Calculate the effective resistance seen looking into the primary of a 20:1 transformer connected to an 8- load.

Your Answer:2.8 k

Correct Answer: 3.2 k

17.

What transformer turns ratio is required to match an 8- speaker load so that the effective load resistance seen at the primary is 12.8 k ?

Your Answer:50:1

Correct Answer: 40:1

18.

Calculate the efficiency of a transformer-coupled class A amplifier for a supply of 15 V and an output of V(p) = 10 V.

Your Answer:50%

Correct Answer: 33.3%

19.

The maximum efficiency of a transformer-coupled class A amplifier is _____. Your Answer:78.5%

Correct Answer: 50%

20.

What is the maximum efficiency of a class B circuit? Your Answer:25%

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21.

How many transistors must be used in a class B power amplifier to obtain the output for the full cycle of the signal?

Your Answer:3

Correct Answer: 2

22.

In class B operation, at what fraction of V_CC should the level of V_L(p) be to achieve the maximum power dissipated by the output transistor?

Your Answer:0.707

Correct Answer: 0.636

23.

Class B operation is provided when the dc bias leaves the transistor biased just off, the transistor turning on when the ac signal is applied.

Your Answer:False

Correct Answer: True

24.

Calculate the efficiency of a class B amplifier for a supply voltage of V_CC = 20 V with peak output voltage of V_L(p) = 18 V. Assume R_L = 16 .

Your Answer: 70.69%

25.

Which of the following is (are) the disadvantage(s) of a class B complementary-symmetry circuit?

Your Answer:It does not provide exact switching of one transistor off and the other on at the zero-voltage condition.

26.

Which of the push-pull amplifiers is presently the most popular form of the class B power amplifier?

Your Answer:Complementary-symmetry

Correct Answer: Quasi-complementary

27.

nMOS and pMOS transistors can be used for class B. Your Answer:False

Correct Answer: True

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Your Answer:83.3%

Correct Answer: 8.33%

29.

Which of the following instruments displays the harmonics of a distorted signal? Your Answer:Oscilloscope

Correct Answer: Spectrum analyzer

30.

Which of the following instruments allows more precise measurement of the harmonic components of a distorted signal?

Your Answer: Wave analyzer

31.

What is the maximum temperature rating for silicon power transistors? Your Answer:250º to 300º

Correct Answer: 150º to 200º

32.

Which of the power amplifiers is not intended primarily for large-signal or power amplification? Your Answer: Class C

33.

Determine what maximum dissipation will be allowed for a 70-W silicon transistor (rated at 25ºC) if derating is required above 25ºC by a derating factor of 0.6 W/ºC at a case

temperature of 100º. Your Answer: 25 W

34.

A silicon power transistor is operated with a heat sink ( _SA = 1.5ºC/W). The transistor, rated at 150 W (25ºC), has _JC = 0.5º C/W, and the mounting insulation has _CS = 0.6 ºC/W. What is the maximum power that can be dissipated if the ambient temperature is 50ºC and T_{Jm ax} = 200 ºC?

Your Answer: 57.7 W

35.

Which of the following transistors has been quite popular as the driver device for class D amplification?

Your Answer:FET

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