Deck 14: Amplifier Frequency Response

Question 1

A BJT amplifier has values of f1B = 5 kHz, f1E = 78 Hz, and f1C = 3.3kHz.What is the overall value of fC1 for the circuit?

A) 3.3 kHz
B) 78 Hz
C) 5 kHz
D) None of these is correct.

Answer 1

5 kHz

Question 2

What frequency is two decades above 5 kHz?

A) 25 kHz
B) 105 kHz
C) 500 kHz
D) Cannot be determined from the information given.

Answer 2

500 kHz

Question 3

Which of the following is an advantage of using dB representations of gain values?

A) Positive and negative dB values represent gain and loss values that are reciprocals of each other.
B) In multistage amplifiers, gain calculations are simplified by the use of dB values.
C) Using dB values, we can represent large gain values with relatively small numbers.
D) All of the above.

Answer 3

All of the above.

Question 4

The bandwidth of an amplifier is

A) the range of frequencies over which gain remains relatively constant.
B) the range of frequencies between its lower and upper 3 dB frequencies.
C) the difference between fc2 -and fc1.
D) All of the above.

Question 5

What frequency lies four octaves above 1 kHz?

A) 8 kHz
B) 16 kHz
C) 9 kHz
D) None of these is correct.

Question 6

An amplifier has values of f0 = 31.6 kHz and fc2 = 1 MHz. What is the approximate value of fc1?

A) 31.6 Hz
B) 1 kHz
C) 178 kHz
D) 12 kHz

Question 7

The roll-off rate for an RC circuit is

A) 20 dB per octave.
B) 6 dB per decade.
C) 6 dB per octave.
D) None of these is correct.

Question 8

A BJT amplifier has values of f2B = 120kHz and f2C = 437 kHz. What is the overall value of fC2 for the circuit?

A) 120 kHz
B) 437 kHz
C) 557 kHz
D) None of these is correct.

Question 9

The high-frequency response of a BJT amplifier is affected by

A) the BJT internal capacitances.
B) the supply voltage VCC).
C) the coupling and bypass capacitor values.
D) All of the above.

Question 10

A BJT amplifier has been analyzed and found to have lower cutoff frequencies of 3.3 kHz, 5 kHz, and 78 Hz. It was also found to have upper cutoff frequencies of 120 kHz, and 437 kHz. What is the overall bandwidth of the amplifier?

A) 115 kHz
B) 432 kHz
C) 119.92 kHz
D) None of these is correct.

Question 11

An amplifier normally has a power gain of 12,000. If the power gain of the circuit drops by 3 dB, the value of Ap will be approximately

A) 6,000.
B) 4,000.
C) 9,000.
D) zero.

Question 12

A common-emitter amplifier has values of Cbc = 5pF and Av = 15. What is the Miller input capacitance for the circuit?

A) 80 pF
B) 7 pF
C) 163.1 pF
D) None of these is correct.

Question 13

The low-frequency response of a BJT amplifier is affected by

A) the BJT internal capacitances.
B) the supply voltage VCC).
C) the coupling and bypass capacitor values.
D) All of the above.

Question 14

Two identical amplifiers are cascaded. The overall bandwidth of the multistage amplifier is the bandwidth of each individual stage.

A) equal to
B) more narrow than
C) wider than

Question 15

An amplifier has values of fc2 = 500 kHz and fc1 = 40 kHz. The center frequency for the circuit is approximately .

A) 141 kHz
B) 230 kHz
C) 270 kHz
D) 460 kHz

Question 16

An amplifier has a midband power gain of 24,500. Which of the following expresses this gain in dB?

A) 87.78 dB
B) 43.9 dB
C) 4.39 dB
D) None of the above.

Question 17

An amplifier has values of Pin = 20 mW and Pout = 60 W. What is the power gain of the circuit?

A) 3000 dB
B) 69.5 dB
C) 34.4 dB
D) None of the above.

Question 18

Negative dB power values represent

A) power gain.
B) power loss.
C) power values that do not change.
D) None of the above.

Question 19

An amplifier has an output power of 500 W. What is the value of ApdB) for the circuit?

A) 26.99 dB
B) 53.98 dB
C) 56.99 dB
D) Cannot be determined from the information given.

Question 20

An amplifier has values of fc1 = 100 kHz and f0 = 200 kHz. What is the value of fc2 for the circuit?

A) 300 kHz
B) 141.4 kHz
C) 400 kHz
D) 460 kHz

Question 21

The value of fC1 for the input circuit of a JFET amplifier is normally that of a comparable BJT amplifier.

A) equal to
B) lower than
C) higher than

Question 22

The equivalent circuit in Figure is used to

A) determine the values of fC1 and fC2.
B) determine the value of fC1.
C) determine the value of fC2.
D) determine none of the values listed here.

Question 23

The transistor amplifier in Figure has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the value if f2C for the circuit?

A) 16.54 kHz
B) 33.02 kHz
C) 330 kHz
D) 7.958 MHz

Question 24

The graph of dB level vs frequency is called a .

A) Body graph
B) Body plot
C) Bode plot
D) All of the above.

Question 25

The circuit in Figure has values of Cbc = 5 pF and Av = 75. What is the value of CoutM) for the circuit?

A) 0.07 pF
B) 5 pF
C) 375 pF
D) 380 pF

Question 26

The transistor amplifier in Figure has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the value of f2B for the circuit?

A) 307.5 kHz
B) 613.8 kHz
C) 6.631 MHz
D) 37.1 MHz

Question 27

The circuit in Figure has values of Cbc = 5 pF and Av = 75. What is the value of CinM) for the circuit?

A) 0.07 pF
B) 5 pF
C) 375 pF
D) 380 pF

Question 28

The transistor amplifier in Figure has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the value of CinM) for the circuit?

A) 6.2 pF
B) 15 pF
C) 1205 pF
D) 2410 pF

Question 29

The portion of the graph labeled ʺeʺ represents .

A) the 3dB cutoff band of frequencies
B) a 20dB/decade roll-off rate
C) a 6 dB/octave response curve
D) bandwidth

Question 30

The transistor amplifier in Figure has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the value of CoutM) for the circuit?

A) 4.979 μF
B) 5pF
C) 1200 pF
D) 1205 pF

Question 31

The component labeled CoutM) in Figure represents the ouput capacitance.

A) medium.
B) MOSFET.
C) modulation.
D) Miller.

Question 32

The transistor amplifier in Figure has the following values: hie = 2 kΩ, hfe = 120, Cbc = 5 pF, Cbe = 10 pF, RS = 300 Ω, Rth = 1.2 kΩ, rc = 4 kΩ, and Cin = 1200 pF. What is the voltage gain of the circuit?

A) 0.24
B) 2
C) 240
D) 480,000