Answer / abdul quadir khumnai

Closed Loop GAIN in presence of POSITIVE FEEDBACK can be
calculate by fomula = Av` = Av/(1-β.Av)

Where,
Av` = closed loop gain.
Av = open loop gain.
β = is feedback ratio

So, according to Barkhausan Criterion

(1) If "β.Av" becomes "unity" i.e., "1". Then, Gain tends to
infinity and Oscillation starts.

(2) and angle between "β" and "Av" must be "0° or 360°"

Answer / apparao

1)The closed loop gain of the amplifier is equal to unity....
2)The total phase shift around the closed loop is equal to
zero degrees or 360 degrees....

Answer / abc

It decides whether a given circuit will oscillate or not,
used in designing of oscillator circuit.

Answer / pavan kumar

it mainly tells that for a I/P INPHASE the feedback o/p
must also be in INPHASE i.e., if I/P IS INPHASE THE OUTPUT
WITH FEEDBACK NEED TO BE IN PHASE

Answer / shoaib

In order to get sustained oscillations it should satisfy magnitude and phase criteria.
magnitode criteria is the total loop gain should be unity.
phase criteria is the total loop phase shift should be either 0 or 360 degrees.

Answer / ali umair khan

i will like to add a little bit to the above excellent posts

first the product of gain and bandwidth should be little
more than 1 at start up otherwise oscillations will not
occurs and as the feedback keeps going after some time it
must be reduced to the value of 1 , so that overdamped
oscillations must not occur, also their must be not any
phase inversion the phase difference b/w i/p and fb should
be 0 and 360 degree.

Answer / aparrna

it is a statement which gives a essential condition to maintain a self sustained oscillation.

Answer / debasis pany

The condition for which oscillation takes place in a
oscillater is known as The Barkhausen Criterion

*SO the total loop gain should be 360 or 0 degree.

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