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  1. #1
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    When is the unity gain feedback loop unstable?

    Hi all!

    When is the unity gain feedback loop unstable? is it when the gain is more than 2, which might implies that the loop feeds the signal of same phase to the input making the negetive loop feedback a positive loop? I am lil confused with this more than 2 gain concept....

    Thanks,
    jackg

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  2. #2
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    Re: When is the unity gain feedback loop unstable?

    I'm not aware of a "more than 2 gain concept". Stability is a matter of loop phase, the gain can be very high. The loop gets exactly unstable when the oscillation condition is met (phase margin = 0), the amplifier will behave bad (overshoot, ringing) if the phase margin gets smaller than about 40 - 50 degree.

    This applies to feedback amplifiers in general, not particularly for unity gain.



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  3. #3
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    Re: When is the unity gain feedback loop unstable?

    When is the unity gain feedback loop unstable? is it when the gain is more than 2

    Perhaps you should reconsider your question.
    A "unity gain feedback loop" with a gain "more than 2" sounds a bit contradictory, does it not?



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