[sdiy] linearize OTA for VCF?

[Jim Patchell]

jhaible at t-online.de wrote:

> Jim Patchell schrieb:
> >     The best (clearest) drawing I have is at
> > http://www.silcom.com/~patchell/jp2rest/dualvco.pdf
> >
> >     There is only 1 LM13700 on the page, so, it is pretty
> > easy to
> > locate.  I used a CA3046 for the current sources, and
> > they also double
> > as the inputs.
>
> Nice circuit. And yes, you got rid of *all* the resistors,
> reproducing the "classic" method. No doubt that this works fine.
> Is it an improovement over National's method ? Extended linear
> range ? Lower offset voltage modulation ? Any other improovement ?
>

    Well, these are all questions I need to answer...I only did a quick
check...And I thought it all worked ok...but that was quite a while ago
now...I will have to get back to that real quick.

    -Jim