more VCO cores

[Haible Juergen]

	> My present solution is to use a BB OPA132 for the op-amp in the
	> converter. 

Thanks for the hint - I've never tried this opamp so far.

	>BTW, I also invented a VCO core that I believe may be unique,
although I
	>never took the time to develop it. A very brief description is in
EN# 111,
	>p.19.

I know. It's based on a differential integrator, and a good idea to build a
triangle
VCO with a pnp expo converter.
I was sceptical when I first saw the circuit, but then I've built it, and it
worked,
and nicely so. I'm not sure how component tolerances would affect the
behaviour.
I have selected resistors and caps to 0.1% to make it foolproof, and I did a
very rough test over 5 Octaves, where it tracked perfectly. This was 2 years
ago, shortly before moving to another house, and then I got acess to cheap
pnp double transitors, so I never did really test its limits. But the brief
glance
I got before the moving was very positive.

JH.