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Discussion in 'Electronic Basics' started by Music Man, Mar 13, 2005.

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  1. Music Man

    Music Man Guest

    How is it that an amp doesn't blow when it has the signal fedback into it in
    circuitry stage?


  2. Good question, given your premise.

    Sometimes amps do blow because of the feedback
    used that was intended to be beneficial. This can
    happen when the output stage cannot handle the
    creation of continuous full-scale AC output, and
    the amplifier becomes unstable once the feedback
    is applied, then oscillates at or near full-scale.

    Nearly all the amplifiers that make it out of the
    development lab are designed to be stable with
    the feedback that is used. And many amplifiers
    are designed to drive their load at full scale on
    a continuous basis without self-destructing.
  3. Internal feedback is ordinarily set up so that it cancels some of the
    normal input signal, effectively reducing what is left to pass through
    the amplifier. This is called negative feedback because of that
    cancellation. Since the feedback comes out of the amplifier, if the
    amplifier is not perfectly linear but amplifies parts of the input
    signal more than other parts, the parts that were amplifier more
    produce mode cancellation, making the net result more linear.

    Positive feedback is that which adds to the normal input signal,
    making it bigger, and also increases the distortion. If positive
    feedback is strong enough, it will make the amplifier an oscillator,
    and it will make its input with no help form any other signal. This
    kind of feedback can seriously overdrive the amplifier and if that
    produces excess heat, can overheat the amplifier.
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