Question 1

Class C amplifiers usually contain

Accepted Answer

A)  two transistors. 
B)  an LC tank circuit in the BJT collector circuit. 
C)  a single BJT that conducts through 360° of the ac input cycle. 
D)  a single BJT that conducts through 270° of the ac input cycle. 
A)  two transistors. 
B)  an LC tank circuit in the BJT collector circuit. 
C)  a single BJT that conducts through 360° of the ac input cycle. 
D)  a single BJT that conducts through 270° of the ac input cycle. B

Question 2

A class AB amplifier has a value of VCC = 15 Vdc. The value of VCEoff) for either transistor is approximately equal to

Accepted Answer

A)  0.7 V. 
B)  5 V. 
C)  7.5 V. 
D)  15 V. 
A)  0.7 V. 
B)  5 V. 
C)  7.5 V. 
D)  15 V. C

Question 3

When properly used, diode bias will prevent

Accepted Answer

A)  crossover distortion and thermal runaway. 
B)  crossover distortion and saturation clipping. 
C)  nonlinear distortion and thermal runaway. 
D)  nonlinear distortion and saturation clipping. 
A)  crossover distortion and thermal runaway. 
B)  crossover distortion and saturation clipping. 
C)  nonlinear distortion and thermal runaway. 
D)  nonlinear distortion and saturation clipping. A

Question 4

-The circuit in Figure  has the following values: VCC = 12 V, R1 = 48 kΩ, R2 = 15 kΩ, RC = 4.7 kΩ, RE = 2.2 kΩ, RL = 12 kΩ, and hfe = hFE = 200 What is the ac cut off voltage for this circuit?

Accepted Answer

A)  6 V 
B)  8.5 V 
C)  12 V 
D)  It cannot be determined with the information given. 
A)  6 V 
B)  8.5 V 
C)  12 V 
D)  It cannot be determined with the information given.

Question 5

A class A amplifier has a compliance of 6 Vpp and a load resistance of 120 Ω. What is the maximum theoretical load power for the circuit?

Accepted Answer

A)  37.5 mW 
B)  300 mW 
C)  50 mW 
D)  100 mW 
A)  37.5 mW 
B)  300 mW 
C)  50 mW 
D)  100 mW

Question 6

A transformer-coupled class A amplifier has a transformer with a 3:1 turns ratio and values of RL = 100 Ω, VCEQ = 6 V, and ICQ = 8 mA. What is the value of vceoff) for the circuit?

Accepted Answer

A)  12 V 
B)  6 V 
C)  13.2 V 
D)  Cannot be determined from the information given. 
A)  12 V 
B)  6 V 
C)  13.2 V 
D)  Cannot be determined from the information given.

Question 7

Which of the following is true?

Accepted Answer

A)  Efficiency is the ratio of dc input power to ac output power. 
B)  The power that an amplifier delivers to its equals the difference between its dc input power and the power that the circuit dissipates. 
C)  Power amplifiers are typically used to drive high impedance loads. 
D)  None of the above statements are true. 
A)  Efficiency is the ratio of dc input power to ac output power. 
B)  The power that an amplifier delivers to its equals the difference between its dc input power and the power that the circuit dissipates. 
C)  Power amplifiers are typically used to drive high impedance loads. 
D)  None of the above statements are true.

Question 8

Figure 11-2
-The circuit in Figure 11-2 is an example of a amplifier.

Accepted Answer

A)  Class A 
B)  Class B 
C)  Class C 
D)  Class AB 
A)  Class A 
B)  Class B 
C)  Class C 
D)  Class AB

Question 9

-The circuit in Figure has the following values: VCC = 12 V, R1 = 48 kΩ, R2 = 15 kΩ, RC = 4.7 kΩ, RE = 2.2 kΩ, RL = 12 kΩ, and hfe = hFE = 200 What is the ac saturation current for this circuit?

Accepted Answer

A)  981 μA 
B)  1.74 mA 
C)  2.53 mA 
D)  It cannot be determined with the information given. 
A)  981 μA 
B)  1.74 mA 
C)  2.53 mA 
D)  It cannot be determined with the information given.

Question 10

An amplifier has values of 2ICQrC = 8.6 V and 2VCEQ = 12 V. If the ac output voltage exceeds 8.6 Vpp, the amplifier will experience

Accepted Answer

A)  saturation clipping. 
B)  cutoff clipping. 
C)  both saturation and cutoff clipping. 
D)  None of the above. 
A)  saturation clipping. 
B)  cutoff clipping. 
C)  both saturation and cutoff clipping. 
D)  None of the above.

Question 11

When troubleshooting a class AB amplifier, you determine that one of the two transistors is faulty. At this point, you should

Accepted Answer

A)  test each of the transistors with an ohmmeter. 
B)  simply replace both transistors. 
C)  look for physical signs of damage to the two transistors. 
D)  test each transistor with a transistor checker. 
A)  test each of the transistors with an ohmmeter. 
B)  simply replace both transistors. 
C)  look for physical signs of damage to the two transistors. 
D)  test each transistor with a transistor checker.

Question 12

Crossover distortion in class B amplifiers is prevented by

Accepted Answer

A)  biasing the transistors deeply into cutoff. 
B)  biasing the transistors slightly above cutoff. 
C)  using complementary-symmetry transistors. 
D)  increasing the load resistance. 
A)  biasing the transistors deeply into cutoff. 
B)  biasing the transistors slightly above cutoff. 
C)  using complementary-symmetry transistors. 
D)  increasing the load resistance.

Question 13

Figure 11-2
-The circuit in Figure 11-2 has the following values: VCC = 16 V, R1 = R2 = 470 Ω, RL = 8 Ω, and hfe = hFE = 200
Determine the values of ICsat) and VCEoff) for the transistors.

Accepted Answer

A)  1 A, 8 V 
B)  2 A, 8 V 
C)  1 A, 16 V 
D)  2 A, 16 V
Chapter 11 Power Amplifiers Answer Key 
A)  1 A, 8 V 
B)  2 A, 8 V 
C)  1 A, 16 V 
D)  2 A, 16 V
Chapter 11 Power Amplifiers Answer Key

Question 14

A class B amplifier has a maximum theoretical efficiency of

Accepted Answer

A)  25%. 
B)  78.5%. 
C)  50%. 
D)  99%. 
A)  25%. 
B)  78.5%. 
C)  50%. 
D)  99%.

Question 15

-A circuit like the one in Figure  has values: I1 = 1 mA, ICQ = 50mA, VCC = 15 V, PP = 9.3 V, and RL = 680 Ω
What is the maximum efficiency of the amplifier?

Accepted Answer

A)  16.62% 
B)  15.9% 
C)  20.8% 
D)  25% 
A)  16.62% 
B)  15.9% 
C)  20.8% 
D)  25%

Question 16

A transformer-coupled class A amplifier has a transformer turns ratio of 4:1 and a load resistance of 25 Ω. The peak-to-peak value of VCE is 12 V. What is the approximate load power for the circuit?

Accepted Answer

A)  45 mW 
B)  160 mW 
C)  90 mW 
D)  60 mW 
A)  45 mW 
B)  160 mW 
C)  90 mW 
D)  60 mW

Question 17

The maximum theoretical efficiency of an RC-coupled class A amplifier is

Accepted Answer

A)  25%. 
B)  50%. 
C)  78.5%. 
D)  99%. 
A)  25%. 
B)  50%. 
C)  78.5%. 
D)  99%.

Question 18

-A circuit like the one in Figure  has values: VCC = 10 V, I1 = 450 μA, and ICQ = 10.55 mA How much power is the circuit drawing from the dc power supply?

Accepted Answer

A)  4.5 mW 
B)  1.21 mW 
C)  110 mW 
D)  Cannot be determined from the information given. 
A)  4.5 mW 
B)  1.21 mW 
C)  110 mW 
D)  Cannot be determined from the information given.

Question 19

A given transistor has a power derating factor of 1.8mW/°C and a power dissipation rating of 400 mW at 25°C. How much power can the device dissipate at 120°C?

Accepted Answer

A)  184 mW 
B)  216 mW 
C)  229 mW 
D)  355 mW 
A)  184 mW 
B)  216 mW 
C)  229 mW 
D)  355 mW

Question 20

The maximum value of VCE in a transformer-coupled class A amplifier will be greater than VCC. This is caused by

Accepted Answer

A)  the input biasing network. 
B)  the efficiency characteristics of the amplifier. 
C)  the counter emf produced by the transformer primary. 
D)  the natural relationship between VCE and VCC. 
A)  the input biasing network. 
B)  the efficiency characteristics of the amplifier. 
C)  the counter emf produced by the transformer primary. 
D)  the natural relationship between VCE and VCC.

Exam 11: Power Amplifiers

Class C amplifiers usually contain

A class AB amplifier has a value of VCC = 15 Vdc. The value of VCEoff) for either transistor is approximately equal to

When properly used, diode bias will prevent

-The circuit in Figure has the following values: VCC = 12 V, R1 = 48 kΩ, R2 = 15 kΩ, RC = 4.7 kΩ, RE = 2.2 kΩ, RL = 12 kΩ, and hfe = hFE = 200 What is the ac cut off voltage for this circuit?

A class A amplifier has a compliance of 6 Vpp and a load resistance of 120 Ω. What is the maximum theoretical load power for the circuit?

A transformer-coupled class A amplifier has a transformer with a 3:1 turns ratio and values of RL = 100 Ω, VCEQ = 6 V, and ICQ = 8 mA. What is the value of vceoff) for the circuit?

Which of the following is true?

Figure 11-2 -The circuit in Figure 11-2 is an example of a amplifier.

-The circuit in Figure has the following values: VCC = 12 V, R1 = 48 kΩ, R2 = 15 kΩ, RC = 4.7 kΩ, RE = 2.2 kΩ, RL = 12 kΩ, and hfe = hFE = 200 What is the ac saturation current for this circuit?

An amplifier has values of 2ICQrC = 8.6 V and 2VCEQ = 12 V. If the ac output voltage exceeds 8.6 Vpp, the amplifier will experience

When troubleshooting a class AB amplifier, you determine that one of the two transistors is faulty. At this point, you should

Crossover distortion in class B amplifiers is prevented by

Figure 11-2 -The circuit in Figure 11-2 has the following values: VCC = 16 V, R1 = R2 = 470 Ω, RL = 8 Ω, and hfe = hFE = 200 Determine the values of ICsat) and VCEoff) for the transistors.

A class B amplifier has a maximum theoretical efficiency of

-A circuit like the one in Figure has values: I1 = 1 mA, ICQ = 50mA, VCC = 15 V, PP = 9.3 V, and RL = 680 Ω What is the maximum efficiency of the amplifier?

A transformer-coupled class A amplifier has a transformer turns ratio of 4:1 and a load resistance of 25 Ω. The peak-to-peak value of VCE is 12 V. What is the approximate load power for the circuit?

The maximum theoretical efficiency of an RC-coupled class A amplifier is

-A circuit like the one in Figure has values: VCC = 10 V, I1 = 450 μA, and ICQ = 10.55 mA How much power is the circuit drawing from the dc power supply?

A given transistor has a power derating factor of 1.8mW/°C and a power dissipation rating of 400 mW at 25°C. How much power can the device dissipate at 120°C?

The maximum value of VCE in a transformer-coupled class A amplifier will be greater than VCC. This is caused by

Fundamental Solid-State Principles

Diodes

Common Diode Applications: Basic Power Supply Circuits

Common Diode Applications: Clippers, Clampers, Voltage Multipliers, and Displays

Special Applications Diodes

Bipolar Junction Transistors

DC Biasing Circuits

Introduction to Amplifiers

Common-Emitter Amplifiers

Other BJT Amplifiers

Field-Effect Transistors

Mosfets

Amplifier Frequency Response

Operational Amplifiers

Additional Op-Amp Applications

Tuned Amplifiers

Oscillators

Solid-State Switching Circuits

Thyristors and Optoelectronics Devices

Discrete and Integrated Voltage Regulators

Filters