>  Have you tried using the cap and/or resistor circuit with a ramp
>  going into it instead of the pulse or square wave?
>  Without going to filtering, this may be the best bet.  I know that
>  in the past I've seen a circuit with a stack of diodes that simulate
>  a sine wave from a square wave by turning on at various amplitudes
>  to imitate the sine function.   But they're ineffecient at best, and
>  they don't produce a very good sine wave.

This is a circuit I've used in various forms. The op amps can be
changed to low power types and the -12V to -5V. It does put out
a pretty good sine wave

http://home.clear.net.nz/pages/joecolquitt/tri2sine.html

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads