[sdiy] square to sine

David G Dixon dixon at mail.ubc.ca
Tue Oct 9 09:26:26 CEST 2012

Hey Team!

I'm looking for a good way to convert square to sine.  I need low-cost,
stable, low-distortion sine wave generators with excellent 1V/octave
tracking over the entire audio range.

I've read the app note for the UAF42 which suggests using a tuned state
variable bandpass filter of moderate Q, but the distortion of this is a
little high for what I want to do (about 1.5% THD).  I'm hoping to get the
THD to less than 0.5%.

One method I'm thinking of is a voltage-controlled clock with divider and
switched capacitor filter.  Has anybody tried this?

I'm not totally averse to digital solutions either, but I'd prefer analog.

Any ideas would be most welcome.

Dave Dixon

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