So is negative feedback more analogous to AGC?
Thanks,
Barry - N4BUQ
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----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@...>
To: [email protected]
Sent: Thursday, March 25, 2021 4:04:37 PM
Subject: Re: [TekScopes] How to explain how negative feedback lowers noise?
Barry,
The sighs were because the idea that negative feedback in an amplifier
reduces noise in the output signal, whether that noise is present in the
input, or is introduced elsewhere in the amplifier, is erroneous. In the
example of noise cancelling headphones the noise is a separate source from
the main signal being amplified. In that case converting the noise signal to
an inverted signal and adding it to the signal of interest does, indeed,
reduce the noise in the summed output, but that bears little relation to the
erroneous idea that negative feedback just reduces noise.
The sighs were specifically because there had been several posts debunking
and bemoaning the error, followed by a post, presumably from someone who had
not read the rest of the thread, modeling exactly the erroneous belief that
had just been debunked and providing a purported explanation that only
served to promote the error.
-- Jeff Dutky
