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#### Bill yg

- Jan 1, 1970

- 0

Perhaps this is a dumb question but I really find confused.

I am building a simple RC-phase shift oscillator using an opamp, with

+/- 15V power supplies. I used a trimmer in the feedback resistor

across the opamp. However, I found something interesting.

The output amplitude is normally +/- 15V. The waveform is somewhat a

fine-looking sine wave.

If I set a larger opamp gain, the output waveform is distorted and

looked like a square wave.

If I set a smaller opamp gain just enough to start oscillation, it

will result in a +/- 12V or smaller sine wave.

The question is:

Why is this so? Why won't the +/- 12V sine wave grow up to +/- 15V?

What I mean is, in theory, the oscillation should grow up to

infinity... and so why now is bounded by +/- VCC? and even with a

smaller gain, bounded by +/- 12V?

Thank you very much.

Billy yg