Barkhausen criteria in multivibrators

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matbob

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Hi,

My question may be absurd but can anyone tell me whether we can apply Barkhusen criteria for astable multivibrators? If it is possible,how?
 

matbob said:
Hi,

My question may be absurd but can anyone tell me whether we can apply Barkhusen criteria for astable multivibrators? If it is possible,how?
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No, you can't.
The reason is simple: The Barkhausen oscillation criterion is based on the loop gain of a circuit with feedback. Any "gain" by definition is a small signal parameter which is valid in the vicinity of an operating point located on a linear (or linearized) portion of the transfer curve.
Multivibrators are strong non-linear circuits which are switched between two extreme values.

(Hint: But I should add that by redesigning the feedback path of a multivibrator the whole circuit can work as a linear oscillator with sinusoidal signals by exploiting the frequency dependent gain of the opamp. But this is beyond your question. Anyhow, this is a very interesting property of the multivibrator structure)
 

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