Oscillator working

[Manu Varkey]

The usual explanation of a feedback oscillator goes like this. ""We have an
Amplifier 'A(w)', a feedback circuit 'B(w)'. An initial input v=Ke(jwt)
produses an output A(w)*B(w)*Ke(jwt) which in turn produces an output
(AB)^2 * Ke(jwt) ...... => If the signal is to be sustained |AB|=1 and
arg(A)+arg(B)=2*pi then each delayed echo or  cycle  of fluctuation
will ‘tack itself onto the tail’ of the previous fluctuation with the same
sinusoidal phase leading to oscillation."" I really don't get it . An
Amplifier produces the output based on instantaneous value of input signal
and there is no mechanism which stores an AC signal. Then how is the
oscillation sustained if the initial disturbance is removed ? Please
correct me if I am wrong.

 

[Charles]

The usual explanation of a feedback oscillator goes like this. ""We have
an
Amplifier 'A(w)', a feedback circuit 'B(w)'. An initial input v=Ke(jwt)
produses an output A(w)*B(w)*Ke(jwt) which in turn produces an output
(AB)^2 * Ke(jwt) ...... => If the signal is to be sustained |AB|=1 and
arg(A)+arg(B)=2*pi then each delayed echo or cycle of fluctuation
will 'tack itself onto the tail' of the previous fluctuation with the same
sinusoidal phase leading to oscillation."" I really don't get it . An
Amplifier produces the output based on instantaneous value of input signal
and there is no mechanism which stores an AC signal. Then how is the
oscillation sustained if the initial disturbance is removed ? Please
correct me if I am wrong.

Noise is what starts the oscillator (or the power-on transient). Also,
inductors and capacitors do store energy and cause the necessary phase
shift. Hope that helps.