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Active Components – Oscillators…


It is the device which changes the DC current to AC current. The output of the oscillator has the constant amplitude. The output frequency may be differed or fixed depending on the design of the oscillator.

Symbol of oscillator:

Types of Oscillators:

  1. According to waveforms generated
Sinusoidal Oscillator

 Relaxation Oscillator


  1. According to fundamental Mechanisms

  • Negative resistance oscillators

It is used to neutralize the positive resistance of oscillator.


  • Feedback Oscillators

Uses the positive feedback to satisfy the bark hausen criteria


  1. According to Frequency generated

Audio frequency oscillator (AFO) Upto 20kHz
Radio frequency oscillator(RFO) 20 kHz to 30 kHz
Very High-frequency oscillator (VHF) 30 MHz to 300MHz
Ultra-high-frequency oscillator (UHF) 300MHz to 3GHz
Microwave frequency Oscillator Above 3 GHZ


4. Depending on the circuit design the sine wave oscillators are classified

a. LC tuned oscillator(operate at high frequency)


Hartley oscillator( the feedback needed for the oscillation is taken from the top of the coil or the junction of the two coils in series)

Colpitts oscillator

Clap oscillator

Tuned collector oscillator
( consists of transformer)

b. RC oscillator (operates at low frequency)


RC phase shift oscillator

Wien Bridge oscillator

Twin-T oscillator

Crystal oscillator

Miller oscillator

Pierce crystal oscillator


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