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Barkhausen criteria basics | First Barkhausen criterion | second Barkhausen criterion

This page describes barkhausen criteria basics. It mentions difference between first Barkhausen criterion and second Barkhausen criterion.

If a negative feedback circuit satisfies following two conditions, the circuit may oscillate at W0.

Barkhausen Criteria

From the above equations, barkhausen criterion can be describes as follows.
• Loop gain A*Β > = 1
• Phase shift around circuit must be 2*π or multiple of 2*π.

First Barkhausen criterion

We typically choose loop gain to be atleast two or three times more than the required value to ensure oscillation in the presence of temperature and other process variations.

Second Barkhausen criterion

The second barkhausen criterion is as follows.
• 180 degree phase shift creterion is equivalent to totally 360 degree loop phase shift.

second barkhausen criterion

• Figure-2a dictates: 180degree phase shift is provided by negative feedback and another 180 degree by amplifier.
• Figure-2b dictates: 360 phase shift is totally provided by amplifier.
• Figure-2c dictates: 2*n8π phase shift function same as figure-2b.

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