Special Purpose Op-Amp Circuits 1 Questions and Answers

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Q31
An active low-pass filter with op-amp commonly uses
  • A RL network
  • B RC network
  • C LC network
  • D Crystal
Answer: Option B
Explanation: Op-amp active filters typically use RC elements for cutoff definition.
Q32
A first-order active low-pass filter roll-off is
  • A 6 dB/octave
  • B 12 dB/octave
  • C 18 dB/octave
  • D 24 dB/octave
Answer: Option A
Explanation: First-order filters attenuate 20 dB/decade, equivalent to 6 dB/octave.
Q33
A first-order high-pass filter has transfer magnitude rising at low frequency at
  • A 6 dB/octave
  • B 12 dB/octave
  • C 0 dB/octave
  • D 24 dB/octave
Answer: Option A
Explanation: The slope near the cutoff is symmetrical to low-pass but increasing.
Q34
A band-pass filter passes
  • A All frequencies
  • B Only low frequencies
  • C Only high frequencies
  • D A limited mid-frequency range
Answer: Option D
Explanation: It allows a defined band around center frequency while attenuating others.
Q35
A notch (band-stop) filter is used to remove
  • A All signals
  • B DC only
  • C A narrow unwanted frequency
  • D Only high frequencies
Answer: Option C
Explanation: Notch filters reject a specific narrow band like 50/60 Hz hum.
Q36
A Wien-bridge oscillator uses an op-amp with
  • A RC lead-lag network
  • B LC tank
  • C Quartz crystal
  • D RL network only
Answer: Option A
Explanation: The RC lead-lag network sets the oscillation frequency in the audio range.
Q37
The condition for oscillation (Barkhausen) requires loop gain
  • A < 1 and 0 degrees phase
  • B = 1 and 0 degrees/360 degrees phase
  • C > 1 and 90 degrees phase
  • D < 1 and 180 degrees phase
Answer: Option B
Explanation: Unity loop gain with net phase shift of 0 degrees/360 degrees sustains oscillations.
Q38
A phase-shift oscillator typically needs how many RC sections for 180 degrees shift
  • A One
  • B Two
  • C Three
  • D Four
Answer: Option C
Explanation: Three identical RC sections provide approximately 180 degrees phase shift with gain.
Q39
A square wave generator often uses an op-amp as a
  • A Comparator with hysteresis
  • B Integrator only
  • C Differentiator only
  • D Voltage follower
Answer: Option A
Explanation: A Schmitt trigger configuration flips states to produce square waves.
Q40
A triangular wave generator can be made using
  • A Two differentiators
  • B Integrator driven by a square wave
  • C Two comparators in series
  • D RC low-pass only
Answer: Option B
Explanation: Integrating a square wave yields a linear triangular waveform.

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