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From: Cursitor Doom <cd999666@notformail.com>
Newsgroups: sci.electronics.design
Subject: The Wien Bridge Oscillator problem  (your Sunday ruined part1)
Date: Sun, 20 Oct 2024 16:36:10 -0000 (UTC)
Organization: A noiseless patient Spider
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Gentlemen,

How critical is the choice of thermistor for a WB oscillator? Stability is 
desired; we know that much (along with minimal distortion of course). The 
usual problem with WB oscillators is they are not amplitude stable and 
either die out or saturate. However, by means of a non-linear negative f/b 
arrangement, they *can* be made stable. One common solution is to use a 
thermistor, usually one with a positive temperature coefficient. The issue 
is, that it must be 'nimble' enough to regulate the output level without 
being *so* 'nimble' as to respond to peaks and troughs of the output 
signal's cycles. I'm going to call this 'nimbleness' "tau" for the time 
being. I know it's not the right Greek letter, but no doubt some helpful 
soul will point out the correct one.
So the question is, how the hell do you select a thermistor with the 
optimum 'tau' for any given wideband WB oscillator?

Your pal,

CD.