Fig. 1 shows a Colpitt’s oscillator. It uses two capacitors and placed across a common inductor
L and the centre of the two capacitors is tapped. The tank circuit is made up of C1, C2 andL. The
frequence of oscillations is determined by the values of C1, C2 and L and is given by;
Note that C1 − C2 − L is also the feedback circuit that produces a phase shift of 180°. Circuit operation.
When the circuit is turn on, the capacitors C1 and C2 are charge. The capacitors discharge through L, setting up oscillations of frequence determined by exp. * (i). The affair voltage of the amplifier appears across C1 and feedback voltage is develop across C2.
The voltage across it's 180 ° out of phase with the voltage develop across C1 (Vout) as show in Fig-2.
It's easy to see that voltage fedback (voltage across C2) to
the transistor provides positive feedback.
A phase shift of 180 ° is produce by the transistor and a farther phase shift of 180 ° is produce by C1 − C2 voltage separator. In this way, feedback is duly phase to produce nonstop
mν. The quantum of feedback voltage in Colpitt’s oscillator depends upon
feedback bit mν of the circuit. For this circuit,
mν = C1/C2
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