boylestad electronics multiple choice q&a chapter (12)

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Site Title: Electronic Devices and Circuit Theory

Summary of Results

Book Author: Boylestad

17% Correct of 35 Score d ite m s:

Location on Site: Chapter 12 > Multiple Choice Date/Time October 12, 2012 at 12:44 AM (UTC/GMT) Submitted:

1.

6 C orre ct:

17%

29 Incorre ct:

83%

More inform ation about scoring

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. Correct Answer: All of the above

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 Correct Answer: Power

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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 Correct Answer: All of the above

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 Correct Answer: C

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13.

Categorize the power efficiency of each class of amplifier, from worst to best. 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 8load resistance seen at the primary is 12.8 k ?

speaker load so that the effective

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% Correct Answer: 78.5%

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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 VC C should the level of VL (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 VC C = 20 V with peak output voltage of VL (p) = 18 V. Assume RL = 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. Correct Answer: All of the above

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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Calculate the harmonic distortion component for an output signal having a fundamental QLS

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amplitude of 3 V and a second harmonic amplitude of 0.25 V. 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 C S = 0.6 ºC/W. What is the maximum power that can be dissipated if the ambient temperature is 50ºC and TJm 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 Correct Answer: MOSFET

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