Q79 / 90 · JEE Main 2022 (26 Jun Shift 2) · Physics

The positive feedback is required by an amplifier to act as an oscillator. The feedback here means

  • A
    External input is necessary to sustain ac signal in output.
  • Correct answer
    B
    A portion of the output power is returned back to the input.
  • C
    Feedback can be achieved by LR network.
  • D
    The base-collector junction must be forward biased.

Solution

When the amplifier connects with positive feedback, it acts as the oscillator. The feedback employed here is positive feedback, this means some amount of the output voltage is given to the input. Hence, the circuit continues its process without any input to the oscillator. The positive feedback is also known as regenerative feedback because the system sustains or regenerates itself without any input source. Hence, the oscillator is nothing but an amplifier with the positive feedback.

Hence, the correct answer is option: 'B'.

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