Tacos Saturday project follow-up : Designing a home lab 1kHz audio Wein bridge op-amp oscillator

[kf4hcw]

On 9/27/21 10:11 PM, samudra.haque at gmail.com wrote:
> But pardon my ignorance, are the harmonics natural and will I see them
> in real life, or just an artifact of the FFT algorithm?

It's a mixed bag. SPICE is nice, but real life curcuits will have
different results.

The theory behind this kind of oscillator is that the gain is
automatically reduced in order to prevent distortions that add
harmonics. You shouldn't need to use 1% components... though you may
need to tweak some things to get the frequency you want.

If the gain part of the circuit is built properly then the diodes will
reduce the gain before adding significant distortion... note that I said
_significant_ here-- they are diodes after all. An incandescent bulb
would be purely resistive (linear) where as the diodes will tend to
conduct exponentially when they begin to conduct. The trick is to get
the gain set so that there is just enough gain to ensure oscillation so
that the diodes only barely start to reduce that gain when the amplitude
of the signal starts to rise -- and that they are able to reduce the
gain sufficiently that the amplitude never rises to anything approaching
the non-linear parts of the op-amp's operating envelope.

You won't get a perfect spectra out of this -- but you should be able to
get something so good that it doesn't matter.

_M

-- 
kf4hcw
Pete McNeil
lifeatwarp9.com/kf4hcw