300+ Active Filter MCQ – Objective Question Answer for Active Filter Quiz

11. Which filter performs exactly the opposite of the band-pass filter?

A. Band-reject filter
B. Band-stop filter
C. Band-elimination filter
D. All of the mentioned

Answer: D

A band rejects is also called a band-stop and band-elimination filter. It performs exactly the opposite of band-pass because it has two passbands: 0 L and f > fH.

 

12. Given the lower and higher cut-off frequency of a band-pass filter are 2.5kHz and 10kHz. Determine its bandwidth.

A. 750 Hz
B. 7500 Hz
C. 75000 Hz
D. None of the mentioned

Answer: B

Bandwidth of a band-pass filter is Bandwidth

= fH– fL=10kHz-2.5kHz

=7.5kHz=7500Hz.

 

13. In which filter the output and input voltages are equal in amplitude for all frequencies?

A. All-pass filter
B. High pass filter
C. Low pass filter
D. All of the mentioned

Answer: A

In an all-pass filter, the output and input voltages are equal in amplitude for all frequencies. This filter passes all frequencies equally well and with phase shift and between the two functions of frequency.

 

14. The gain of the first order low pass filter

A. Increases at the rate 20dB/decade
B. Increases at the rate 40dB/decade
C. Decreases at the rate 20dB/decade
D. Decreases at the rate 40dB/decade

Answer: C

The rate at which the gain of the filter changes in the stopband is determined by the order of the filter. So, for a low pass filter, the gain decreases at the rate of 20dB/decade.

 

15. Which among the following has the best stop band response?

A. Butterworth filter
B. Chebyshev filter
C. Cauer filter
D. All of the mentioned

Answer: C

The cauer filter has a ripple passband and a ripple stopband. So, generally, the cauer filter gives the best stop band response among the three.

 

16. Determine the order of filter used, when the gain increases at the rate of 60dB/decade on the stopband.

A. Second-order low pass filter
B. Third-order High pass filter
C. First-order low pass filter
D. None of the mentioned

Answer: B

The gain increases for the high pass filter. So, for a third-order high pass filter, the gain increases at the rate of 60dB/decade in the stopband until f=fL.

 

17. Name the filter that has two stopbands?

A. Band-pass filter
B. Low pass filter
C. High pass filter
D. Band-reject filter

Answer: A

A band-pass filter has two stop bands: 1) 0 < f < fL and 2) f > fH.

 

18. The frequency response of the filter in the stopband.

A. Decreases with increase in frequency
B. Increase with an increase in frequency
C. Decreases with a decrease in frequency
D. All of the above

Answer: C

The order of frequency of the filter in the stopband determines either steady decreases or increases or both with an increase in frequency.

 

19. Find the voltage across the capacitor in the given circuit

Find the voltage across the capacitor in the given circuit


A. VO= Vin/(1+0.0314jf)
B. VO= Vin × (1+0.0314jf)
C. VO= Vin+0.0314jf/(1+jf)
D. None of the mentioned

Answer: A

The voltage across the capacitor,

VO= Vin/(1+j2πfRC)

=> VO= Vin/(1+j2π × 5k × 1µF × f)

=> VO= Vin/(1+0.0314jf).

 

20. Find the complex equation for the gain of the first order low pass Butterworth filter as a function of frequency.

A. AF/[1+j(f/fH)].
B. AF/√ [1+j(f/fH)2].
C. AF × [1+j(f/fH)].
D. None of the mentioned

Answer: A

The gain of the filter, as a function of frequency, is given as

VO/ Vin=A F/(1+j(f/fH)).

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