#### Re: Confused about how AGC works?

Jerry Gaffke

Barkhausen stability criterion is dense.
If you find an explanation that is sufficient to do design work without being dense, do let us know!
There are thousands of 3'rd year undergraduate electrical engineering students who want to see it.

> Does the delay in part prevent oscillations by introducing a phase shift?

Specifying a delay at a given frequency is equivalent to specifying a phase shift.
For example, a 1khz audio signal has a period of 1 millisecond.
If we put it through a delay line that delays it by 0.5 milliseconds,
then the output of the delay line is phase shifted 180 degrees with respect to the input.

Jerry, KE7ER

On Fri, Apr 19, 2019 at 02:36 PM, digger AB3XU wrote:
Thanks Don and Jerry for your explanations. In my OP I wasn't thinking about that what I described were oscillations, and as you wrote the parts are chosen to stabilize the circuit and prevent that. Does the delay in part prevent oscillations by introducing a phase shift?

Jerry, the initial link you posted Barkhausen stability criterion was a bit dense for me, but your summary  was useful. Even so it lead me to read some on feedback loops which was helpful.

Don, you are certainly right, I could understand the simple theory of your circuit but got lost on the complexity of how it actually works.

73, digger

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