[sdiy] VCO unstable in Spice, stable in real world

[David G. Dixon]

> Bringing the reset comparator output uhh... 'out' can be troublesome. You
> can easily inject noise onto the comparator output from the outside world
> and screw up the VCO reset.

Yes.

> I'd buffer that output if possible, a 4000 series CMOS gate would do well
> and the propagation delay of 50ns (max for a 4069 on 15V supply) is 
> unlikely to be a problem.

Awesome suggestion!  I suppose you could invert the comparator output with
CMOS as well without adding significant delay, if you needed the inverted
version for whatever reason.  The only problem is that you've then got five
spare buffers on the 4069 chip.

> Of course, don't forget to add a 1K series resistor on that output :^)