Question 1

A BJT has measured values of IB = 1 mA and IC = 80mA. When IB is varied by ±100 μA, IC changes by ±10 mA. What is the value of ac beta for the device?

Accepted Answer

A)   80
B)   10
C)   100
D)   800 C

Question 2

A CE amplifier has values of VB = 5 V and RE = 2 kΩ. What is the value of rʹe for the transistor?

Accepted Answer

A)   10 Ω
B)   5 Ω
C)   11.7 Ω
D)   Cannot be determined with the information given. C

Question 3

The input and output signal currents for a common-emitter amplifier are

Accepted Answer

A)   always 180° out of phase.
B)   180° out of phase in all but one amplifier configuration.
C)   in phase in all but one amplifier configuration.
D)   always in phase. D

Question 4

The common-emitter amplifier provides

Accepted Answer

A)   voltage gain, current gain, and power gain.
B)   voltage gain and power gain, but no current gain.
C)   current gain and power gain, but no voltage gain.
D)   current gain and voltage gain, but no power gain.

Question 5

-What is the approximate value of Zbase?

Accepted Answer

A)   2.77 kΩ
B)   4.62 kΩ
C)   27.6 kΩ
D)   45.8 kΩ

Question 6

-If the 8.2 kΩ and 1.5 kΩ biasing resistors are changed to 16 kΩ and 3 k Ω respectively, the circuit voltage gain

Accepted Answer

A)   Increases.
B)   Decreases.
C)   Does not change significantly.

Question 7

-What is the value of Av for the amplifier?

Accepted Answer

A)   400
B)   150
C)   200
D)   33.33

Question 8

A transistor has the following values: hfe = 120, hFE = 200, hie = 5 kΩ, hre = 4 × 10-4, and hoe = 2500 μS. What is the value of rʹe for the device?

Accepted Answer

A)   4 × 10-4 Ω
B)   41.7 Ω
C)   400 Ω
D)   25 Ω

Question 9

A BJT has measured values of IB = 1 mA and IC = 80mA. When IB is varied by ±100 μA, IC changes by ±10 mA. What is the value of dc beta for the device?

Accepted Answer

A)   80
B)   10
C)   100
D)   800

Question 10

-A common-emitter amplifier may be swamped to

Accepted Answer

A)   decrease the input impedance of an amplifier.
B)   reduce variations in voltage gain.
C)   increase the value of Av for an amplifier.
D)   cause all of the above to occur.

Question 11

A swamped amplifier has values of hie = 3 kΩ, hfe = 150, hFE = 200, rE = 300 Ω, and RE = 1.2 kΩ.
What is the value of Zbase for the circuit?

Accepted Answer

A)   3 kΩ
B)   183 kΩ
C)   48 kΩ
D)   None of these are correct.

Question 12

-What is the approximate value of Av?

Accepted Answer

A)   22.2
B)   170
C)   5
D)   None of the above are correct.

Question 13

-What is the value of Zbase for the circuit in Figure ?

Accepted Answer

A)   3.75 kΩ
B)   300 kΩ
C)   5 kΩ
D)   400 kΩ

Question 14

Which of the following conditions would indicate that an emitter bypass capacitor is open?

Accepted Answer

A)   The presence of a dc voltage at the emitter terminal of the BJT
B)   The presence of an ac voltage at the emitter terminal of the BJT
C)   The loss of the ac signal at the base terminal of the BJT
D)   None of the above.

Question 15

The disadvantage of swamping a CE amplifier is that it

Accepted Answer

A)   increases voltage gain.
B)   decreases voltage gain.
C)   increases input impedance.
D)   decreases input impedance.

Question 16

A BJT has values of hFE = 200 and hfe = 120. The ac current gain for the device is

Accepted Answer

A)   200.
B)   120.
C)   24,000.
D)   320.

Question 17

-The amplifier has a value of VE = 1.1 V. What is the approximate value of Av for the circuit?

Accepted Answer

A)   11
B)   110
C)   485
D)   Cannot be determined with the information given

Question 18

A CE amplifier is constructed using RC = 3.3 kΩ and RL = 12 kΩ. The transistor has the ~
Following specifications: hfe = 120, hie = 5 kΩ, hre = 4 × 10=4, and hoe = 2500 μS. What is the
Value for Av for this amplifier?

Accepted Answer

A)   Approximately 62.2
B)   Approximately 79.1
C)   Approximately 287.8
D)   None of the above.

Question 19

If a bypass capacitor opens, the value of rʹe

Accepted Answer

A)   increases.
B)   decreases.
C)   does not change.

Question 20

-What is the approximate value of Zin?

Accepted Answer

A)   867
B)   992 Ω
C)   1.21 kΩ
D)   None of the above.

Exam 9: Common-Emitter Amplifiers