Phase Shift Oscillator
Fig-1 shows the circuit of a phase shift oscillator. It consists of a conventional single transistor
amplifier and a RC phase shift network. The phase shift network consists of three sections R1C1, R2C2
. and R3C3. At some particular frequency f0, the phase shift in each RC section is 60º so that the total
. Phase- shift produced by the RC network is 180º.
The frequency of oscillations is give by
When the circuit is switch on, it produces oscillations of frequency determined by exp. (i). The affair E0 of the amplifier is fed back to RC feedback network. This network
produces a phase shift of 180º and a voltage Ei
appears at its affair which is applied to the transistor
Obviously, the feedback bit m = Ei/ E0.
The feedback phase is correct.
A phase shift of 180º
is produced by the transistor amplifier. A further phase shift of 180º is produce by the RC network.
As a result, the phase shift around the entire circle is 360º.
(i) It does n’t bear manufactories or inductors.
( ii) It can be use to produce truly low frequence.
(iii) The circuit provides good frequency stability.
(i) It’s delicate for the circuit to start oscillations as the feedback is generally small.
(ii) The circuit gives small affair.
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