# Active Components – Oscillators…

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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)

Types:

 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)

Types

 RC phase shift oscillator Wien Bridge oscillator Twin-T oscillator Crystal oscillator Miller oscillator Pierce crystal oscillator