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From: ISW@cup.portal.com (Isaac S Wingfield)
Newsgroups: sci.electronics
Subject: Re: Sine wave generator
Message-ID: <21924@cup.portal.com>
Date: 6 Sep 89 20:39:10 GMT
References: <790@serene.UUCP>
Distribution: usa
Organization: The Portal System (TM)
Lines: 14

Greg Bell writes:

I'm going to all this trouble.  In addition, how do the sine wave generators
that use the PTC of a particular light bulb work???                          

The light bulb's non-linear resistance is (hopefully) used to
control the amplitude of the oscillation to keep the amp in
it's linear region (necessary for good sines). Messers Hewlett
and Packard made a bunch of money off that kind of oscillator!

For the doorbell, try a big L-C set up for damped ringing (sorry)
Maybe you can synthesize the L from an op-amp.

Isaac    isw@cup.portal.com