Practice Exam Test Questions
Choose the letter of the best answer in each questions.
1. The critical frequency is defined as the point at which the response drops _________ from the passband.
- A. –20 dB
- B. –3 dB
- C. –6 dB
- D. –40 dB
2. Which filter exhibits a linear phase characteristic?
- A. Bessel
- B. Butterworth
- C. Chebyshev
- D. all of the above
3. Which filter has a maximally flat response?
- A. Bessel
- B. Butterworth
- C. Chebyshev
- D. all of the above
4. Which filter exhibits the most rapid roll-off rate?
- A. Bessel
- B. Butterworth
- C. Chebyshev
- D. all of the above
5. A third-order filter will have a roll-off rate of
- A. –20 dB/decade.
- B. –40 dB/decade.
- C. –60 dB/decade.
- D. –30 dB/decade.
6. Refer to Figure 15-1. Identify the frequency response curve for a band-reject filter.
Figure 15-1
- A. a
- B. b
- C. c
- D. d
7. Refer to Figure 15-1. Identify the frequency response curve for a low-pass filter.
- A. a
- B. b
- C. c
- D. d
8. Refer to Figure 15-1. Identify the frequency response curve for a high-pass filter.
- A. a
- B. b
- C. c
- D. d
9. Refer to Figure 15-1. Identify the frequency response curve for a band-pass filter.
- A. a
- B. b
- C. c
- D. d
10. Refer to Figure 15-2(a). This is a _____ filter, and it has a cutoff frequency of _____.
Figure 15-2
- A. high-pass, 21 Hz
- B. low-pass, 21 Hz
- C. high-pass, 2.65 kHz
- D. low-pass, 2.65 kHz
11. Refer to Figure 15-2(b). The cutoff frequency of this filter is _____, and the circuit is known as a _____.
- A. 721 Hz, low-pass filter
- B. 721 Hz, high-pass filter
- C. 72 Hz, low-pass filter
- D. 721 Hz, band-pass filter
12. Refer to Figure 15-2(c). This is a _____ filter.
- A. band-pass
- B. band-stop
- C. high-pass
- D. low-pass
13. Refer to Figure 15-2(d). This circuit is known as a _____ filter, and the fc is _____.
- A. high-pass, 1.59 kHz
- B. band-pass, 15.9 kHz
- C. low-pass, 15.9 kHz
- D. high-pass, 15.9 kHz
14. Refer to Figure 15-2(b). RA = 2.2 kΩ and RB = 1.2 kΩ. This filter is probably a
- A. Butterworth type.
- B. Bessel type.
- C. Chebyshev type.
- D. none of the above
15. Refer to Figure 15-2(c). The roll-off of this filter is about
- A. 20 dB/decade.
- B. 40 dB/decade.
- C. 60 dB/decade.
- D. 80 dB/decade.
16. Refer to Figure 15-2(a). The roll-off of the circuit shown is about
- A. 20 dB/decade.
- B. 40 dB/decade.
- C. 60 dB/decade.
- D. 80 dB/decade.
17. A low-pass filter has a cutoff frequency of 1.23 kHz. Determine the bandwidth of the filter.
- A. 2.46 kHz
- B. 1.23 kHz
- C. 644 Hz
- D. not enough information given
18. Refer to Figure 15-3. This is a _____ filter.
Figure 15-3
- A. low-pass
- B. high-pass
- C. band-pass
- D. band-stop
19. Refer to Figure 15-3. This filter has a roll-off rate of
- A. 20 dB/decade.
- B. 40 dB/decade.
- C. 60 dB/decade.
- D. 80 dB/decade.
20. Refer to Figure 15-3. Increasing the values of the filter section resistors in this circuit will cause the fc to
- A. increase.
- B. decrease.
- C. remain the same.
- D. increase and then decrease.
21. The bandwidth in a _____ filter equals the critical frequency.
- A. low-pass
- B. high-pass
- C. band-pass
- D. band-stop
22. A _____ filter significantly attenuates all frequencies below fc and passes all frequencies above fc.
- A. low-pass
- B. high-pass
- C. band-pass
- D. band-stop
23. A _____ filter passes all frequencies within a band between a lower and an upper critical frequency and rejects all others outside this band.
- A. low-pass
- B. high-pass
- C. band-pass
- D. band-stop
24. A _____ filter rejects all frequencies within a specified band and passes all those outside this band.
- A. low-pass
- B. high-pass
- C. band-pass
- D. band-stop
25. Filters with the _____ characteristic provide a very flat amplitude in the passband and a roll-off rate of –20 dB/decade/pole.
- A. Butterworth
- B. Chebyshev
- C. Bessel
- D. none of the above
26. Filters with the _____ characteristic are useful when a rapid roll-off is required because it provides a roll-off rate greater than –20/dB/decade/pole.
- A. Butterworth
- B. Chebyshev
- C Bessel
- D. none of the above
27. Filters with the _____ characteristic are used for filtering pulse waveforms.
- A. Butterworth
- B. Chebyshev
- C. Bessel
- D. none of the above
28. The gain of the multiple-feedback band-pass filter above is equal to which of the following? Assume C = C1 = C2.
- A. A0 = R2 / R1
- B. A0 = R1 / R2
- C. A0 = R2 / 2 R1
- D. A0 = R1 / 2 R2
29. One important application of a state-variable _____ filter with a summing amplifier is to minimize the 60 Hz "hum" in audio systems.
- A. low-pass
- B. high-pass
- C. band-pass
- D. band-stop
TRUE/FALSE
1. The bandwidth of a band-pass filter is the sum of the two cutoff frequencies.
- A. True
- B. False
2. Butterworth filters have the characteristic of a very flat response in the passband and a roll-off of –20 dB/decade.
- A. True
- B. False
3. Filters with Bessel characteristics are used for filtering pulse waveforms.
- A. True
- B. False
4. In filters, a single RC network is called a pole.
- A. True
- B. False
5. A band-pass filter passes all frequencies within a band between a lower and an upper cutoff frequency.
- A. True
- B. False
6. The bandwidth of a practical high-pass filter is infinite.
- A. True
- B. False
7. A second-order filter has a roll-off of –20 dB/decade.
- A. True
- B. False
8. A Sallen-Key filter is a second-order filter.
- A. True
- B. False
9. An active filter uses capacitors and inductors in the feedback network.
- A. True
- B. False
10. A band-pass filter can be created by cascading a high-pass filter and a low-pass filter.
- A. True
- B. False
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