feedback

- L
- Larry Brasfield
  
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posted
19 years ago

Sun, Mar 13, 2005 5:47 PM

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.

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--Larry Brasfield
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- M
- Music Man
  
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posted
19 years ago

Mon, Mar 14, 2005 1:33 AM

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

Thanks

- J
- John Popelish
  
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posted
19 years ago

Mon, Mar 14, 2005 5:52 AM

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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John Popelish