[sdiy] VCO Cap Switch

Jay Schwichtenberg jays at aracnet.com
Tue Jun 4 18:25:24 CEST 2002


I love this group, I was going through major withdrawal when it was down.

I was looking into the reset circuits in VCOs and have some questions. I'll
also say I'm more into stability of the oscillator than exact waveforms.

First I was looking into using the 2N7000 as the FET to reset the cap.
They're easily available. In the archives there are a couple of things
mentioned that left me a bit confused.

Basically is the capacitance and leakage current for the 2N7000 an issue for
what we're doing?

Has anyone used them in their VCOs?

Next is the comparator. Most designs use LM311 and LM393 comparators, but
some the faster LM319.

Any comments on this?

Isn't it also more important to have a consistent reset time than a short
reset time if you aren't that critical of the waveforms?

Also what should we keep the reset time under?

Thanks in advance.

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