[sdiy] VCO - sine output - why bother?

[mskala at ansuz.sooke.bc.ca]

On Mon, 29 Aug 2016, Ian Fritz wrote:
> Yes, that's why I abandoned the COTA approach in favor of the limit-cycle
> approach. For the four-stage version, the waves are all the same amplitude,

Where can I find more information about this "limit cycle approach"?  I
did some Google searching and all I found was academic literature from
chaos theory, where the term seems to refer to any dynamical system whose
behaviour converges on some kind of cycle.  There's a more precise
mathematical definition, but it doesn't seem useful:  my reading of it is
that almost any electronic oscillator could be called a "limit cycle"
oscillator, and there'd be no specific reason for that to give especially
pure sine waves unless the oscillator happens to be designed so that the
limit cycle is a pure sine wave, which is begging the question.

The specific design of your own that you're pointing to seems to differ
from other oscillators in that it's applying gentle limiting at all
amplitudes increasing slowly with greater amplitude instead of harder
limiting almost zero at low amplitude and increasing quickly at high
amplitude, and it applies the limiting at all stages instead of just one.
Are those the important features of the "limit cycle approach"?

-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before principles.
http://ansuz.sooke.bc.ca/