Circuits and Resonance Questions and Answers

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Q31
What is the typical efficiency of class B push-pull amplifier?
  • A 25%
  • B 50%
  • C 78.5%
  • D 95%
Answer: Option C
Explanation: Class B has theoretical efficiency of 78.5%
Q32
The main advantage of negative feedback in amplifiers is:
  • A Increases gain
  • B Reduces bandwidth
  • C Increases distortion
  • D Improves stability
Answer: Option D
Explanation: Negative feedback improves stability and reduces distortion
Q33
In a Hartley oscillator, the feedback is obtained from:
  • A Capacitive divider
  • B Inductive divider
  • C Resistive divider
  • D Direct coupling
Answer: Option B
Explanation: Hartley uses inductive voltage divider for feedback
Q34
What is cross-over distortion in class B amplifiers?
  • A High frequency distortion
  • B Zero-crossing distortion
  • C Thermal distortion
  • D Phase distortion
Answer: Option B
Explanation: Distortion at zero-crossing due to transistor turn-on delay
Q35
The Q-point in transistor amplifiers is set to:
  • A AC operating point
  • B DC operating point
  • C Peak current point
  • D Breakdown point
Answer: Option B
Explanation: Q-point establishes DC operating point for proper amplification
Q36
In RC phase shift oscillator, the phase shift per RC section is:
  • A 30°
  • B 45°
  • C 60°
  • D 90°
Answer: Option C
Explanation: Each RC section provides approx 60° phase shift, total 180°
Q37
What is the main use of a Schmitt trigger?
  • A Amplification
  • B Voltage regulation
  • C Waveform shaping
  • D Power amplification
Answer: Option C
Explanation: Schmitt trigger is used for waveform shaping and noise immunity
Q38
The Barkhausen criterion for oscillations is:
  • A Aβ = 0
  • B Aβ = 1
  • C Aβ ≥ 1 with 0° phase
  • D Aβ ≤ 1 with 180° phase
Answer: Option C
Explanation: |Aβ| ≥ 1 and phase shift = 0° or 360°
Q39
In a differential amplifier, CMRR stands for:
  • A Common Mode Rejection Ratio
  • B Common Mode Resistance Ratio
  • C Current Mode Rejection Ratio
  • D Capacitive Mode Rejection Ratio
Answer: Option A
Explanation: Common Mode Rejection Ratio measures differential gain/common mode gain
Q40
What is the purpose of a heat sink in power amplifiers?
  • A Increase gain
  • B Reduce noise
  • C Dissipate heat
  • D Store energy
Answer: Option C
Explanation: Heat sinks dissipate heat to prevent thermal runaway

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