Colpitts oscillator theory can be used for radio frequency (RF), that its output signal are often utilized at the basis of wireless communication system in most application.
Dear Omar,
The Colpitts oscillator is a tuned circuit oscillator that can generate sinusoidal signals in the radio frequency range. Such oscillator consists of a positive feed back amplifier with the collector load is a tuned circuit composed of a an inductor in parallel with a capacitive voltage divider. A part of the output voltage on the larger capacitor of the divider is positively fed back to the input of the amplifier which may be the emitter of a common base transistor amplifier:http://www.learnabout-electronics.org/Oscillators/osc23.php
The Colpitts oscillator theory is based on the Barkhausen stability criterion:
where a positive feed back amplifier can produce sustained oscillations if A beta>=1, with A is the gain of the amplifier, and beta is the positive feed back factor. This implies two conditions as A and Beta are complex numbers. That is mag. Abeta =1 and the phase of the oscillating loop = 2 pi,
The CB colpitts oscillator given in figure to satisfy the second condition of the phase the resonance circuit at the collector must be in resonance and the feed back capacitor must act only a blocking capacitor with its reactance is negligible at the resonance frequency.
The other condition that that one has to adjust mag. A beta =1 with
according to the equivalent circuit of the transistor and the circuit theory A= gain of the amplifier at resonance= gm ( 1/gm II RE) ((C2+C3)/C3))^2,
Beta= C3/(C3+C2)
Best wishes
Thank you Professor Abdehalim Zekry for this clarification.@Abdelhalim Zekry
On a side note, one interesting property of Colpitts oscillator is its ability to produce Chaotic Signals. Chaotic signals have interesting properties and have been utilized for implemented security at the physical level of communication.
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