You could have a sine and square wave oscillator with 4 opamps.  All you
have to do is construct the first two as integrators, the third as an
inverting amp and feed back the output into the input of the first
integrator.  This gives you a sine wave.  Then use the last amp as a zero
crossing to convert to a square wave.

Will send you a diagram off list if you need further clarification.

Brian.

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of picdude
Sent: 27 October 2003 06:30
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]: Simple function generator circuit?


I need a simple squarewave generator with a range of 0 Hz to ~5kHz.  I tried
breadboarding a simple 555 circuit, but it's horrendously unstable (the
freq-counter is not thr problem).

So far in books or on the web, the ones I've seen are built around
specialized chips (8038, MAX038, XR2206, etc), that are not available
locally nor at Digikey.

Anyone here know of a simple circuit that will handle this requirement?
Accurate freq output is not important, but stability is, and sine/triangle
is not important, but perhaps I could use it sometime in the future.

Cheers,
-Neil.

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