Deck 8: Introduction to Amplifiers

Question 1

Which BJT amplifier configuration typically provides the lowest input impedance?

A) The common emitter amplifier
B) The common base amplifier
C) The common collector amplifier

Answer 1

The common base amplifier

Question 2

An amplifier with a value of Av = 20 dB. What input voltage is required for the amplifier to provide an 8.5 V output?

A) 850 mV
B) 85 mV
C) 425 mV
D) 186 mV

Answer 2

850 mV

Question 3

An amplifier has signal values of vin = 30 mV and vout = 1.8 V. What is the voltage gain of the amplifier?

A) 30
B) 0.06
C) 60
D) 54

Answer 3

60

Question 4

An ideal amplifier has Zout.

A) infinite
B) low
C) zero
D) high

Question 5

An amplifier is driven by a 200 mV source with an internal resistance RS) of 50 Ω. If Zin is 150 Ω, what is the value of vin?

A) 600 mV
B) 66.7 mV
C) 50 mV
D) 150 mV

Question 6

An ideal amplifier has Zin.

A) infinite
B) low
C) zero
D) high

Question 7

Which BJT amplifier configuration typically provides the highest power gain?

A) The common emitter amplifier
B) The common base amplifier
C) The common collector amplifier

Question 8

An amplifier draws 1.8 W from its dc power supply and delivers 250 mW to its load. What is the efficiency of the amplifier?

A) 45%
B) 13.9%
C) 87.8%
D) 12.2%

Question 9

An amplifier has values of Av = 300 and vout = 2.63 V. What is the magnitude of the amplifier input voltage?

A) 786 mV
B) 8.77 mV
C) 8.77 μV
D) 114 mV

Question 10

An amplifier with an efficiency rating of 18% draws 3.25 W from its dc power supply. What is the maximum power it can deliver to its load?

A) 585 mW
B) 55 mW
C) 18 W
D) 58.5 mW

Question 11

Assuming the source voltage is constant, vin if Zin decreases.

A) increases
B) decreases
C) remains unchanged

Question 12

Which class of amplifier conducts throughout 360° of its input signal?

A) Class A
B) Class B
C) Class C

Question 13

Which class of amplifier has the highest efficiency?

A) Class A
B) Class B
C) Class C

Question 14

Assuming the source voltage is constant, vL if Zin decreases.

A) increases
B) decreases
C) remains unchanged

Question 15

Effective voltage gain is always Av.

A) greater than or equal to
B) less than or equal to
C) equal to

Question 16

The amplifier in Figure has the following values: Zout = 1.2 kΩ, RL = 3.3 kΩ, vout = 18.6 V. What is the value of the load voltage?

A) 13.6 V
B) 6.78 V
C) 51.3 V
D) 4.07 V

Question 17

What is the dB power gain of an amplifier if Av = 20dB and Rin and Rout are equal?

A) 20dB
B) 10dB
C) -3dB
D) 40dB

Question 18

An amplifier with a 100 mW input provides a 3.25 W output . What is the power gain of the amplifier?

A) 30.2 dB
B) -4.9 dB
C) 4.9 dB
D) 15.1 dB

Question 19

A amplifier is normally a tuned amplifier.

A) Class A
B) Class B
C) Class C

Question 20

Assuming the circuit voltage gain is constant, what happens to vL when Zout decreases?

A) It increases
B) It decreases
C) It remains unchanged

Question 21

A class B amplifier is subject to:

A) non-linear distortion.
B) crossover distortion.
C) class C interference.
D) Answer A and B
Chapter 8 Introduction to Amplifiers Answer Key

Question 22

Which of the following circuit values is greater than the other two?

A) Voltage gain Av)
B) Current gain Ai)
C) Power gain Ap)

Question 23

An amplifier contains a single transistor with an LC tank in its collector circuit. The amplifier is most likely a/an

A) Tuned amplifier.
B) Voltage-divider amplifier.
C) Emitter follower.
D) Reactance amplifier.

Question 24

This circuit would have relatively Zin and Zout.

A) low; low
B) midrange; midrange
C) high; high
D) low; high
E) high; low

Question 25

An amplifier has two transistors, one npn and one pnp. The transistor emitters are connected to each other and to the load. The amplifier is most likely a

A) Common Emitter amplifier.
B) Class A amplifier.
C) Class B amplifier.
D) Class C amplifier.

Question 26

This circuit would have relatively Zin and Zout.

A) low; low
B) low; high
C) high; low
D) high; high

Question 27

The circuit in Figure is a amplifier.

A) Common emitter
B) Common collector
C) Common base
D) Class C

Question 28

This circuit is a

A) Class A amplifier
B) Class B amplifier
C) Class C amplifier
D) Common base amplifier

Question 29

Which of the following circuit values is greater than the other two?

A) Voltage gain Av)
B) Current gain Ai)
C) Power gain Ap)

Question 30

The circuit in Figure is a amplifier.

A) Common emitter
B) Common collector
C) Common base
D) Class C