Re: Random thoughts on sinewave oscillators

On Fri, 18 Oct 2024 09:48:17 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Edward Rawde <invalid@invalid.invalid> wrote:
>

Is the reason why this doesn't produce a better looking sinewave because
the amplifier slew rate is faster going down than it is going up or some
other reason?
 
Ignore the wild decoupling, it took me long enough to get the concept to
work at all.
 
I'm aware that a single package containing two op amps could probably do a
much better job.

>
if noise is more important than waveform, I found amplitude control by
clipping gave the lowest noise.  The oscillators in this...
>
<http://www.poppyrecords.co.uk/other/DistortionMeter/intermodmeter.htm>
>
...are amplitude stabilised by clipping.

If the gain of an oscillator loop is close to 1.00, say 0.98 to 1.02,
one can add in a small tweak, a crude multiplier or even a clipper, to
make up the difference.

Of course, with many-bit DACs being cheap nowadays, it's easier to do
a DDS sine wave generator, and get super-precise frequency and
amplitude. A 70 cent uP can do that, and even use PWM to eliminate the
DAC.

All sorts of elegant analog circuits are blown away by cheap digital
junk. Sigh.