GATE Electrical – Analog Electronics
Practice Problems – Page 18
This section contains problems based on Oscillators and feedback principles.
Problem 171
Question:
What is an oscillator?
Answer:
An oscillator is an electronic circuit that generates periodic signals without any external input signal.
Problem 172
Question:
What are the two essential conditions for oscillation?
Answer:
- Loop gain must be equal to 1
- Total phase shift must be 360° or 0°
This is known as Barkhausen Criterion.
Problem 173
Question:
Write the frequency formula of an RC phase shift oscillator.
Answer:
f = 1 / (2πRC√6)
Problem 174
Question:
What is the frequency formula of Wien bridge oscillator?
Answer:
f = 1 / (2πRC)
Problem 175
Question:
Which oscillator is commonly used for audio frequency generation?
Answer:
Wien Bridge Oscillator
Problem 176
Question:
Why is positive feedback required in oscillators?
Answer:
To sustain continuous oscillations.
Problem 177
Question:
If R = 10 kΩ and C = 0.01 μF, find frequency of Wien bridge oscillator.
Solution:
f = 1 / (2πRC)
RC = 10,000 × 0.01 × 10⁻⁶
f ≈ 1591 Hz
Problem 178
Question:
Which oscillator uses three RC sections?
Answer:
RC Phase Shift Oscillator
Problem 179
Question:
What type of feedback is used in oscillators?
Answer:
Positive feedback
Problem 180
Question:
Which device is commonly used as amplifier in RC oscillator?
Answer:
Transistor or Operational Amplifier.
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