Deck 10: Amplifier Frequency Response

Question 1

The voltage gain of an amplifier is 200. The decibel voltage gain is

A)23 dB.
B)200 dB.
C)46 dB.
D)106 dB.

Answer 1

C

Question 2

At the lower or upper cutoff frequency, the voltage gain is

A)0.707 Avmid.
B)0.995 Avmid.
C)0.35 Avmid.
D)0.5 Avmid.

Answer 2

A

Question 3

Refer to the figure above. If RL increases in value, the output voltage would

A)decrease.
B)remain the same.
C)increase.
D)Cannot be determined.

Answer 3

C

Question 4

At the unity- gain frequency, the open- loop voltage gain is

A)very large.
B)Amid.
C)1.
D)zero.

Question 5

Refer to the figure above. If the output voltage at the upper cutoff frequency was 7.19 Vp- p, the output voltage that would be expected at the lower cutoff frequency is

A)2.11 Vp- p.
B)5.08 Vp- p.
C)7.19 Vp- p.
D)10.17 Vp- p.

Question 6

If an amplifier has an input signal voltage of 0.37 mV and an output voltage of 16.8 V, the voltage gain in dB would be

A)45.4 dB.
B)33.1 dB.
C)46.6 dB.
D)93.1 dB.

Question 7

Refer to the figure above. The capacitance Cbc affects

A)mid- range response.
B)low- frequency response.
C)high- frequency response.
D)nothing.

Question 8

If the voltage gain doubles, the decibel voltage gain increases by

A)10 dB.
B)3 dB.
C)6 dB.
D)a factor of 2.

Question 9

A Bode plot

A)provides a visual presentation of decibel voltage gain vs. frequency.
B)indicates voltage gain only at 0 Hz.
C)indicates voltage gain with no reference to frequency.
D)is a testing method used for dc amplifiers.

Question 10

At low frequencies, the emitter- bypass capacitor

A)increases the output voltage.
B)is no longer an ac short.
C)increases the voltage gain.
D)has minimum XC.

Question 11

If the power gain doubles, the decibel power gain increases by

A)6 dB.
B)a factor of 2.
C)3 dB.
D)10 dB.

Question 12

What effect does low frequency have on the emitter bypass RC circuit?

A)Decreases impedance and decreases voltage gain
B)Increases impedance and increases voltage gain
C)Decreases impedance and increases voltage gain
D)Increases impedance and decreases voltage gain

Question 13

If an amplifier has a bandwidth of 47 kHz and a higher cutoff frequency of 104 kHz, the lower cutoff frequency would be

A)151 kHz.
B)104 kHz.
C)47 kHz.
D)57 kHz.

Question 14

The voltage gain of an amplifier is 150. If the output voltage doubles for the same amount of input voltage), the voltage gain equals

A)49.5 db.
B)43.5 db.
C)21.7 db.
D)114 db.

Question 15

Refer to the figure above. The bandwidth of this amplifier is

A)the lower frequency times 0.707.
B)the difference between the upper and lower frequencies.
C)the sum of the upper and lower frequencies.
D)the upper frequency divided by 0.707.

Question 16

In the midband of a CE amplifier

A)the voltage gain is maximum.
B)the coupling and bypass capacitors appear open.
C)the emitter is not at ac ground.
D)the Miller effect has maximum influence.

Question 17

At low frequencies, the coupling capacitors produce a decrease in

A)generator voltage.
B)generator resistance.
C)voltage gain.
D)input resistance.

Question 18

A high pass filter may be used to

A)pass high frequencies.
B)pass frequencies between low and high.
C)pass low frequencies.
D)Both A and B above.

Question 19

A roll- off of 20 dB per decade is equivalent to a roll- off of _ per octave.

A)12 dB
B)13 dB
C)6 dB
D)3 dB

Question 20

Which of the following capacitances affects the high frequency response of an amplifier?

A)Stray wiring capacitance
B)Internal pn junction capacitance
C)Coupling and bypass capacitors
D)Both A and B above.

Question 21

The fc of a certain RC network that has values of R = 470 ▲ and C = 0.005 µF is

A)425 kHz.
B)213 kHz.
C)12 kHz.
D)67.7 kHz.

Question 22

If an amplifier has an output voltage of 12.7 Vp- p at the midpoint of the frequency range, the output voltage at the cutoff frequency would be

A)12.7 Vp- p.
B)5.89 Vp- p.
C)8.98 Vp- p.
D)4.49 Vp- p.

Question 23

Refer to the figure above. The output voltage at fcl is 22 mV. Ideally, Vout at the midpoint frequency would be

A)17 mV.
B)31.1 mV.
C)22 mV.
D)Not enough information to determine.

Question 24

Refer to the figure above. High frequency response is affected by

A)RC.
B)C3.
C)CBE.
D)All of the above.

Question 25

If an amplifier has an Rin = 950 ▲, and a coupling capacitor of value 3.3 µF, the approximate cutoff frequency would be

A)50.8 kHz.
B)5.08 Hz.
C)50.8 Hz.
D)508 Hz.

Question 26

The cutoff frequency of a low pass filter occurs at

A)- 3 dB.
B)+3 dB.
C)- 20 dB.
D)- 5 dB.

Question 27

Semilog graph paper has

A)one vertical linear axis and one logarithmic horizontal axis.
B)two 2)linear axes.
C)two 2)logarithmic axes.
D)one horizontal linear axis and one vertical logarithmic axis.

Question 28

The unity- gain frequency fT)equals the product of mid- range voltage gain AVmid))and the

A)compensating capacitance.
B)BW.
C)fcu.
D)load resistance.

Question 29

Phase shift in the input of an RC circuit will approach 90° when frequency approaches

A)maximum.
B)zero.
C)cutoff.
D)mid- range.

Question 30

For a lag network above the cutoff frequency, the voltage gain

A)decreases at the rate of 6 db per octave.
B)increases at the rate of 6 db per octave.
C)decreases at the rate of 20 db per decade.
D)A and C above.

Question 31

The frequency response of an amplifier is a graph of

A)input voltage versus frequency.
B)voltage versus current.
C)voltage versus time.
D)output voltage versus frequency.

Question 32

If the value of a feedback capacitor is 50 pF, what is the input Miller capacitance when AV = 200?

A)1 µF
B)10 µF
C)10 nF
D)100 µF

Question 33

Refer to the figure above. Low frequency response is affected by

A)CBE.
B)C3.
C)RC.
D)All of the above.

Question 34

If an amplifier has a voltage gain of 54 dB, and an input signal of 22 mV, the output signal voltage would be

A)24.5 V.
B)2.45 V.
C)55.3 V.
D)11 V.

Question 35

Raising the frequency of 1 kHz by 2 octaves results in a frequency of

A)250 Hz.
B)2 MHz.
C)500 Hz.
D)4 kHz.

Question 36

The critical frequencies of an amplifier are the frequencies where the output voltage is

A)0.707 of Vmid.
B)0.25 of Vmid.
C)half of Vmid.
D)zero.