Fast analog sw. as VC resistor

[Christopher_List at Sonymusic.Com]

...uhhh, please ignore my last post - I see it's already been covered
<mental note: read all email thoughly before replying :)>

I would, however, still like to know what the frequency of your sawtooth
was...
I guess it was less than 10Khz?

> I'm going to get some LM339's and try them.

Reminder:  LM339's can SINK current, but cannot SOURCE it. You need to use
a pull-up resistor on the output. I went nuts the first time I used one of
these chips until I realized what was going on...

It also might help to have a little positive feedback (like a resistor in
the 560K to 1M range between the output and +in) on the comparator to speed
it up.

A slightly better general purpose op-amp - like a TL084 or LF412 should be
able to handle stuff up to at least 50 or 100kHz no problem - right?
Actually, an LM358 would be better for driving the CMOS switch - how fast
can they go?

I would think that the higher the frequency the better - because it would
be easier to filter out - yes?

- CList