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Active Filters

1. 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

Answer: Option D

2. Identify the frequency response curve for a band-pass filter.

A. a B. b

C. c D. d

Answer: Option A

3. 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

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C. Bessel

Answer: Option B

4. 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

Answer: Option B

5.

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

Answer: Option C

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6. Refer to the given figure. 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

Answer: Option D

7. The bandwidth in a ________ filter equals the critical frequency.

A. low-pass B. high-pass

C. band-pass D. band-stop

Answer: Option A

8. Filters with the ________ characteristic are used for filtering pulse waveforms.

A. Butterworth B. Chebyshev

C. Bessel

Answer: Option C

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9. Refer to the given figure. The roll-off of this filter is about

A. 20 dB/decade.

B. 40 dB/decade.

C. 60 dB/decade.

D. 80 dB/decade.

Answer: Option A

10. Refer to the given figure. 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.

Answer: Option A

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11. Refer to this figure. This is a ________ filter.

A. low-pass B. high-pass

C. band-pass D. band-stop

Answer: Option B

12. Which filter exhibits a linear phase characteristic?

A. Bessel

B. Butterworth

C. Chebyshev

D. all of the above

Answer: Option A

13. Refer to the given figure. The cutoff frequency of this filter is ________, and the circuit is

known as a ________.

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A. 721 Hz, low-pass filter

B. 721 Hz, high-pass filter

C. 72 Hz, low-pass filter

D. 721 Hz, band-pass filter

Answer: Option A

14. 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

Answer: Option B

15. 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

Answer: Option A

16. Which filter exhibits the most rapid roll-off rate?

A. Bessel

B. Butterworth

C. Chebyshev

D. all of the above

Answer: Option C

17. Which filter has a maximally flat response?

A. Bessel

B. Butterworth

C. Chebyshev

D. all of the above

Answer: Option B

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18. Identify the frequency response curve for a high-pass filter.

A. a B. b

C. c D. d

Answer: Option B

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19. Identify the frequency response curve for a low-pass filter.

A. a B. b

C. c D. d

Answer: Option C

20. Refer to the given figure. This is a ________ filter.

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A. band-pass B. band-stop

C. high-pass D. low-pass

Answer: Option A

21. 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

Answer: Option B

22. Refer to this figure. 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.

Answer: Option B

23. 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

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Answer: Option D

24. Refer to the given figure. This is a ________ filter, and it has a cutoff frequency of

________.

A. high-pass, 21 Hz

B. low-pass, 21 Hz

C. high-pass, 2.65 kHz

D. low-pass, 2.65 kHz

Answer: Option C

25. Refer to the given figure. RA = 2.2 k and RB = 1.2 k . This filter is probably a

A. Butterworth type.

B. Bessel type.

C. Chebyshev type.

Answer: Option A

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26. Refer to this figure. This filter has a roll-off rate of

A. 20 dB/decade.

B. 40 dB/decade.

C. 60 dB/decade.

D. 80 dB/decade.

Answer: Option D

27. Identify the frequency response curve for a band-reject filter.

A. a B. b

C. c D. d

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Answer: Option D

28. 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.

Answer: Option C

29. 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

Answer: Option C

TRUE OR FALSE

1. A band-pass filter can be created by cascading a high-pass filter and a low-pass filter.

A. True B. False

Answer: Option A

2. The bandwidth of a band-pass filter is the sum of the two cutoff frequencies.

A. True B. False

Answer: Option B

3. A Sallen-Key filter is a second-order filter.

A. True B. False

Answer: Option A

4. Filters with Bessel characteristics are used for filtering pulse waveforms.

A. True B. False

Answer: Option A

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5. The bandwidth of a practical high-pass filter is infinite.

A. True B. False

Answer: Option B

6. In filters, a single RC network is called a pole.

A. True B. False

Answer: Option A

7. A band-pass filter passes all frequencies within a band between a lower and an upper cutoff

frequency.

A. True B. False

Answer: Option A

8. An active filter uses capacitors and inductors in the feedback network.

A. True B. False

Answer: Option B

9. A second-order filter has a roll-off of 20 dB/decade.

A. True B. False

Answer: Option B

10. 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

Answer: Option A