Unit 4 – Feedback & Oscillators

English – Part B (2-mark) Short Answer Questions and Answers

1. What is an oscillator?
   Generates AC signal from DC supply without input.
2. Advantages of negative feedback.
   Stabilizes gain, reduces distortion, increases bandwidth.
3. Define feedback in amplifiers.
   Feeding part of output back to input (positive or negative).
4. What is Wien bridge oscillator?
   RC bridge oscillator producing pure sine wave.
5. Four types of negative-feedback amplifiers.
   Voltage series, voltage shunt, current series, current shunt.
6. How many RC sections in RC phase-shift oscillator?
   Three sections for 180° phase shift.
7. What is negative feedback?
   Feedback out of phase with input; reduces gain; improves stability.
8. What is Barkhausen criterion?
   Loop gain = 1 and phase shift = 0° or 360° for oscillation.
9. What is a tank circuit?
   LC network that stores energy in magnetic and electric fields.
10. What is positive feedback?
    Feedback in phase with input; increases gain; used in oscillators.

Tamil – Part B (2-mark) Short Answer Questions and Answers

1. What is an oscillator?
   DC supply இல் இருந்து AC signal generate செய்யும் circuit.
2. Advantages of negative feedback.
   Gain stable ஆகும், distortion reduce ஆகும், bandwidth increase ஆகும்.
3. Define feedback in amplifiers.
   Output இல் ஒரு பகுதி input க்கு feed பண்ணுவது ( positive அல்லது negative ).
4. What is Wien bridge oscillator?
   RC bridge network use பண்ணி pure sine wave produce செய்யும் oscillator.
5. Four types of negative feedback amplifiers.
   Voltage series, Voltage shunt, Current series, Current shunt.
6. RC phase shift oscillator இல் எத்தனை RC sections use பண்ணப்படும்?
   மூன்று RC sections 180° phase shift கிடைக்க use பண்ணப்படும்.
7. What is negative feedback?
   Feedback signal input க்கு out of phase ; gain reduce ஆகும் – stable output கிடைக்கும்.
8. What is Barkhausen Criterion?
   Loop gain = 1 மற்றும் total phase shift = 0° அல்லது 360° ஆக இருக்க வேண்டும்.
9. What is tank circuit?
   L மற்றும் C network energy store செய்யும் circuit.
10. What is positive feedback?
    Feedback input க்கு in-phase ; gain increase ஆகும் – oscillator இல் use செய்யப்படுகிறது.