VCO using ICL8038

Jim Patchell patchell at
Thu Nov 11 16:26:04 CET 1999

    You can use the 8038 to make a modulation source, but as a pitch source,
it is pretty bad.  It is not at all accurate enough for music.  A long time
ago I tried this chip, as well as the XR2207 chip, which is a lot better
than the 8038, but still, no where near good enough for a pitch source.

Andy Main wrote:

> Hi all,
> Has anyone tried making a VCO using the Harris chip ICL8038 (see
> This is a precision waveform generator, allow PWM of sine, triangle
> (allows adjustment of slope for previous discussions), and square.

> Obviously it'll need other circuitry to change it to be 1V/Oct CV but it
> is temperature stable (altiough it does run hot), ie no need to
> dismantle any cruise missiles to get the temcos !!! Or find matched
> pairs etc etc.

    Actually, start looking for the cruise missiles.  What makes a VCO
unstable with temperature is the exponential converter.  My suggestion is if
you are looking for VCO circuits, go to TomG's website and pick one of
those.  I discovered a long time ago that there was no easy way (of the
shelf) to make a VCO, except for the CEM3340 vco chip, which while
temporaily availiable again from Paul Schrieber (sp?), there is no reliable
source for a good VCO chip.

> Appreciate any responses, and I've ordered one for testing for my
> modular design.
> Andy

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