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:
- According to waveforms generated
| Sinusoidal Oscillator
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Relaxation Oscillator
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According to fundamental Mechanisms
It is used to neutralize the positive resistance of oscillator.
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Uses the positive feedback to satisfy the bark hausen criteria |
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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)
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| Colpitts oscillator
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| Clap oscillator
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| Tuned collector oscillator ( consists of transformer)  |
b. RC oscillator (operates at low frequency)
Types
| RC phase shift oscillator
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| Wien Bridge oscillator
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| Twin-T oscillator
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| Crystal oscillator
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| Miller oscillator
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| Pierce crystal oscillator
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