Which type of feedback is used in case of an oscillator circuit?

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RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 2)
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  1. Zero
  2. Positive
  3. Negative
  4. Unity

Answer (Detailed Solution Below)

Option 2 : Positive
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Detailed Solution

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Oscillators

An oscillator is a circuit that produces a continuous, repeated, alternating waveform without any input.

Oscillators basically convert unidirectional current flow from a DC source into an alternating waveform.

Oscillators work on positive feedback and follow Bark hausen's criteria.

The Barkhausen stability criterion is a mathematical condition to determine when a linear electronic circuit will oscillate or not. It will oscillate when:

  • The loop gain must be unity.
  • The phase shift through the loop is either zero or an integer multiple of 2π.

Types of oscillators on basis of frequency

Type of Oscillator   

Approximate frequency range
Crystal oscillator Fixed frequency
Tickler feedback oscillator Nearly fixed frequency
Wien bridge oscillator 1 Hz to 1 MHz
Phase-shift oscillator 1 Hz to 10 MHz
Hartley's oscillator  10 kHz to 100 MHz
Colpitt's oscillator  10 kHz to 100 MHz
 
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