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Active Filters MCQs

Practice Active Filters MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1
Analog ElectronicsActive Filters

A high-pass filter ideally attenuates signals primarily?

  • AAbove its cutoff frequency
  • BBelow its cutoff frequency
  • COnly exactly at resonance
  • DAt all frequencies equally
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Correct Answer: B. Below its cutoff frequency
Explanation: A high-pass filter passes frequencies above its cutoff region while attenuating lower-frequency components.
Reference: Standard analog electronics: active filters
Question 2
Analog ElectronicsActive Filters

A band-pass filter is intended primarily to?

  • APass a selected range of frequencies and attenuate frequencies outside it
  • BPass DC only
  • CReject only one exact frequency with no passband
  • DAmplify every frequency equally
Report an error
Correct Answer: A. Pass a selected range of frequencies and attenuate frequencies outside it
Explanation: A band-pass response passes frequencies between lower and upper cutoff frequencies while attenuating frequencies outside that band.
Reference: Standard analog electronics: active filters
Question 3
Analog ElectronicsActive Filters

An ideal first-order low-pass active filter has a cutoff frequency of 1 kHz. At frequencies far above cutoff, its magnitude rolls off asymptotically at approximately?

  • A-10 dB/decade
  • B-20 dB/decade
  • C-40 dB/decade
  • D+20 dB/decade
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Correct Answer: B. -20 dB/decade
Explanation: Each first-order pole contributes an asymptotic attenuation slope of about -20 dB per decade beyond the cutoff region.
Reference: Standard analog electronics: active filters
Question 7
Analog ElectronicsActive Filters

A second-order Butterworth low-pass filter is known for having which passband characteristic?

  • AMaximally flat magnitude response
  • BEqual ripple in the passband
  • CA notch at DC
  • DInfinite gain at cutoff
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Correct Answer: A. Maximally flat magnitude response
Explanation: The Butterworth approximation is designed for a maximally flat magnitude response in the passband.
Reference: Standard analog electronics: active filters
Question 8
Analog ElectronicsActive Filters

In a first-order passive RC low-pass network, the magnitude of the transfer function at the cutoff frequency is approximately what fraction of its low-frequency value?

  • A0.5
  • B0.707
  • C1.0
  • D1.414
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Correct Answer: B. 0.707
Explanation: At the cutoff frequency of a first-order RC network, the magnitude is 1/sqrt(2), approximately 0.707 of the passband value.
Reference: Standard analog electronics: first-order filter cutoff
Question 9
Analog ElectronicsActive Filters

A first-order high-pass filter with cutoff frequency 1 kHz is operated at 100 Hz, one decade below cutoff. Its asymptotic gain relative to the passband is approximately?

  • A-3 dB
  • B-10 dB
  • C-20 dB
  • D-40 dB
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Correct Answer: C. -20 dB
Explanation: A first-order high-pass response rises at about 20 dB/decade below cutoff, so one decade below cutoff the asymptotic attenuation is about 20 dB.
Reference: Standard analog electronics: high-pass filter response
Question 13
Analog ElectronicsActive Filters

Compared with a Butterworth filter of the same order, a Chebyshev Type I filter generally provides?

  • AA sharper transition at the cost of passband ripple
  • BNo passband ripple and slower transition in every case
  • CZero phase shift
  • DNo frequency selectivity
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Correct Answer: A. A sharper transition at the cost of passband ripple
Explanation: Chebyshev Type I uses equal-ripple passband behavior to obtain a steeper transition than a comparable Butterworth design.
Reference: Standard analog electronics: Chebyshev filter
Question 14
Analog ElectronicsActive Filters

A Bessel filter is often selected when the main requirement is good preservation of waveform shape because it emphasizes?

  • AApproximately linear phase and nearly constant group delay in the passband
  • BMaximum passband ripple
  • CInfinite stopband attenuation at cutoff
  • DNegative resistance
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Correct Answer: A. Approximately linear phase and nearly constant group delay in the passband
Explanation: Bessel responses are valued for nearly constant group delay and good transient behavior, helping preserve pulse and waveform shape.
Reference: Standard analog electronics: Bessel filter
Question 17
Analog ElectronicsActive Filters

A notch filter is designed primarily to?

  • AStrongly attenuate a narrow band around a selected frequency
  • BPass only DC and reject all AC
  • CAmplify every frequency equally
  • DGenerate a sinusoidal signal without input
Report an error
Correct Answer: A. Strongly attenuate a narrow band around a selected frequency
Explanation: A notch, or band-stop, filter produces strong rejection around a chosen frequency while passing frequencies on either side.
Reference: Standard analog electronics: notch filter