Explore topic-wise MCQs in Active Filter Circuits.

This section includes 111 Mcqs, each offering curated multiple-choice questions to sharpen your Active Filter Circuits knowledge and support exam preparation. Choose a topic below to get started.

51.

One condition for positive feedback is that the phase shift around the feedback loop must be ________°.

A. 0
B. 90
C. 180
D. 45
Answer» B. 90
Discussion
52.

Refer to this figure. Assuming it is configured as an oscillator and if you desired to reduce the duty to less than 50%, the following circuit change would need to be made.

A. Reduce the size of R1.
B. Reduce the size of R2.
C. Increase the size of R1.
D. Connect a diode in parallel with R1.
Answer» E.
Discussion
53.

Refer to this figure. Determine the frequency of oscillation, if any.

A. 131 Hz
B. 262 Hz
C. 2.62 kHz
D. none
Answer» B. 262 Hz
Discussion
54.

Refer to this figure. This circuit is

A. a sine-wave oscillator.
B. a monostable multivibrator.
C. an astable multivibrator.
D. a VCO.
Answer» D. a VCO.
Discussion
55.

Refer to this figure. What is the duty cycle, if any?

A. 16.3%
B. 54.5%
C. 86.9%
D. none
Answer» C. 86.9%
Discussion
56.

Refer to this figure. If C1 increases in value, the resonant frequency will

A. increase.
B. decrease.
C. remain the same.
Answer» C. remain the same.
Discussion
57.

Refer to the given figure. The resonant frequency is controlled by

A. C3 and L1.
B. C2, C4, C5, and L1.
C. C3, C4, C5, and L1.
D. C3, C4, C5, and L2.
Answer» D. C3, C4, C5, and L2.
Discussion
58.

Refer to this figure. Determine the resonant frequency.

A. 123.4 kHz
B. 61.7 kHz
C. 45.94 kHz
D. 23.1 kHz
Answer» D. 23.1 kHz
Discussion
59.

Refer to this figure. Calculate the resonant frequency.

A. 1.126 kHz
B. 6.17 kHz
C. 23.9 MHz
D. 14.1 MHz
Answer» C. 23.9 MHz
Discussion
60.

Calculate the fr of a lead-lag network if R1 = R2 = 6.8 k, and C1 = C2 = 0.05 F.

A. 468 Hz
B. 4.68 kHz
C. 46.8 kHz
D. 468 kHz
Answer» B. 4.68 kHz
Discussion
61.

One condition for positive feedback is that the phase shift around the feedback loop must be _______degree;

A. 45
B. 0
C. 180
D. 90
Answer» C. 180
Discussion
62.

Calculate the resonant frequency of this oscillator.

A. 1560.34 Hz
B. 3120.70 Hz
C. 4681.07 Hz
D. 6241.37 Hz
Answer» B. 3120.70 Hz
Discussion
63.

The frequency distortion arising because of varying amplifier gain with frequency is considerably reduced in a negative-voltage feedback amplifier circuit.

A. True
B. False
C. -
D. -
Answer» B. False
Discussion
64.

An op-amp integrator has a square-wave input. The output should be

A. a sine wave.
B. a triangle wave.
C. a square wave.
D. pure dc.
Answer» C. a square wave.
Discussion
65.

What is the relationship between the series and parallel resonant frequencies of a quartz crystal?

A. They are equal.
B. Parallel resonant frequency is approximately 1 kHz higher than series resonant frequency.
C. Series resonant frequency is approximately 1 kHz higher than parallel resonant frequency.
D. none of the above
Answer» C. Series resonant frequency is approximately 1 kHz higher than parallel resonant frequency.
Discussion
66.

Which of the following is (are) feedback?

A. Voltage-series
B. Voltage-shunt
C. Current-series
D. All of the above
Answer» E.
Discussion
67.

Calculate the f r of a lead-lag network if R 1 = R 2 = 6.8 k , and C 1 = C 2 = 0.05 F.

A. 468 Hz
B. 4.68 kHz
C. 46.8 kHz
D. 468 kHz
Answer» B. 4.68 kHz
Discussion
68.

At parallel resonance, the impedance of a crystal is

A. minimum.
B. maximum.
C. equal.
D. zero.
Answer» C. equal.
Discussion
69.

A certain oscillator has a tap on the inductor in the tank circuit. This oscillator is probably

A. a Colpitts oscillator.
B. a Clapp oscillator.
C. a crystal oscillator.
D. a Hartley oscillator.
Answer» E.
Discussion
70.

Determine the input impedance with feedback for a voltage-series feedback having A = –100, R 1 = 15 k , R o = 20 k , and a feedback of = –0.25.

A. 110 k
B. 290 k
C. 390 k
D. 510 k
Answer» D. 510 k
Discussion
71.

In the Wien bridge oscillator, which of the following is (are) frequency-determining components?

A. R 1 and R 2
B. C 1 and C 2
C. R 1 , R 2 , C 1 , and C 2
D. None of the above
Answer» D. None of the above
Discussion
72.

What is the typical value of quality factor for crystal oscillators?

A. 20,000
B. 1000
C. 100
D. 10
Answer» B. 1000
Discussion
73.

Referring to this figure, calculate the amplification gain with feedback for the following circuit values: R 1 = 80 k , R 2 = 20 k , R o = 10 k , R D = 61 k , and g m = 4000 ?S.

A. –4.36
B. –4.25
C. –6.35
D. –20.85
Answer» B. –4.25
Discussion
74.

The twin-T oscillator produces a ________ response.

A. low-pass
B. high-pass
C. band-pass
D. band-stop
Answer» E.
Discussion
75.

For frequencies up to 1 MHz, the ________ is the most widely used type of sinusoidal RC oscillator.

A. Wien-bridge
B. phase-shift
C. twin-T
D. -
Answer» B. phase-shift
Discussion
76.

At series resonance, the impedance of a crystal is

A. minimum.
B. maximum.
C. equal.
D. zero.
Answer» B. maximum.
Discussion
77.

In the IC phase-shift oscillator, what should the ratio of feedback resistor R f to R 1 be?

A. Zero
B. Greater than –29
C. Less than 29
D. Any value
Answer» C. Less than 29
Discussion
78.

The start-up gain of an oscillator must be ________ one.

A. equal to
B. less than
C. greater than
D. -
Answer» D. -
Discussion
79.

The lead-lag circuit in the Wien-bridge oscillator has a resonant frequency at which the attenuation is

A. 1/2.
B. 1/4.
C. 1/3.
D. 1/5.
Answer» D. 1/5.
Discussion
80.

An input signal is needed for an oscillator to start.

A. True
B. False
C. -
D. -
Answer» C. -
Discussion
81.

What is the total phase shift requirement, around the feedback loop, for a phase-shift oscillator?

A. 90°
B. 180°
C. 270°
D. 360°
Answer» E.
Discussion
82.

The Nyquist plot combines the two Bode plots of gain versus frequency and phase shift versus frequency on a single plot.

A. True
B. False
C. -
D. -
Answer» B. False
Discussion
83.

Calculate the resonant frequency of this Wien bridge oscillator if R 1 = 25 k , R 2 = 40 k , C 1 = 0.001 F, and C 2 = 0.002 F.

A. 1560.3 Hz
B. 1779.4 Hz
C. 3120.7 Hz
D. 3558.8 Hz
Answer» E.
Discussion
84.

Determine the voltage gain with feedback for a voltage-series feedback having A = –100, R 1 = 15 k , R o = 20 k , and a feedback of = –0.25.

A. 3.85
B. –3.85
C. –9.09
D. 9.09
Answer» C. –9.09
Discussion
85.

Determine the output impedance with feedback for a voltage-series feedback having A = –100, R 1 = 15 k , Ro = 20 k , and a feedback of = –0.25.

A. 0.2 k
B. 392.16
C. 1.82 k
D. 769.23
Answer» E.
Discussion
86.

At what phase shift is the magnitude of A at its minimum in the Nyquist plot?

A. 90º
B. 180º
C. 270º
D. 0º
Answer» E.
Discussion
87.

Referring to this figure, calculate the voltage gain with feedback A vf .

A. –4.85
B. –4.20
C. –4.17
D. –4.00
Answer» D. –4.00
Discussion
88.

One condition for positive feedback is that the phase shift around the feedback loop must be ________°.

A. 0
B. 90
C. 180
D. 45
Answer» B. 90
Discussion
89.

Referring to this figure, calculate the amplification gain where the op-amp gain (A) is 200,000, R 1 = 1.5 k , and R 2 = 400 .

A. 4.25
B. 4.50
C. 4.75
D. 5.00
Answer» D. 5.00
Discussion
90.

What is the ratio of the output impedance with series feedback to that without feedback?

A. 1
B. 1 + A
C. A
D. A
Answer» C. A
Discussion
91.

Which of the following oscillators is (are) tuned oscillators?

A. Colpitts
B. Hartley
C. Crystal
D. All of the above
Answer» E.
Discussion
92.

The amplifier is unstable if the Nyquist curve plotted encloses (encircles) the –1 point, and it is stable otherwise.

A. True
B. False
C. -
D. -
Answer» B. False
Discussion
93.

In order to start up, a feedback oscillator requires

A. negative feedback less than 1.
B. positive feedback greater than 1.
C. unity feedback equal to 1.
D. no feedback.
Answer» C. unity feedback equal to 1.
Discussion
94.

A circuit that can change the frequency of oscillation with an application of a dc voltage is sometimes called

A. a voltage-controlled oscillator.
B. a crystal oscillator.
C. a Hartley oscillator.
D. an astable multivibrator.
Answer» B. a crystal oscillator.
Discussion
95.

Which of the following is required for oscillation?

A. A > 1
B. The phase shift around the feedback network must be 180º.
C. Both A > 1 and the phase shift around the feedback network must be 180º.
D. None of the above
Answer» D. None of the above
Discussion
96.

Referring to this figure, calculate the voltage gain with the feedback for the following circuit values: R D = 4 k , R S = 1 k , R F = 15 k , and g m = 5000 ?S.

A. –11.2
B. –8.57
C. –6.75
D. –3.25
Answer» C. –6.75
Discussion
97.

Sinusoidal oscillators operate with ________ feedback.

A. positive
B. negative
C. -
D. -
Answer» B. negative
Discussion
98.

The feedback signal in a(n) ________ oscillator is derived from a capacitive voltage divider in the LC circuit.

A. Hartley
B. Armstrong
C. Colpitts
D. -
Answer» D. -
Discussion
99.

An amplifier with a gain of –500 and a feedback of = –0.1 has a gain change of 15% due to temperature. Calculate the change in gain of the feedback amplifier.

A. 0.2%
B. 0.3%
C. 0.4%
D. 0.5%
Answer» C. 0.4%
Discussion
100.

What is the minimum frequency at which a crystal will oscillate?

A. seventh harmonic
B. third harmonic
C. fundamental
D. second harmonic
Answer» D. second harmonic
Discussion