[sdiy] linearize OTA for VCF?

[patchell]

    Hmm....I used current sources to run the diodes on a 13700 and I thought I
didn't have any problem...maybe I better go back and take a look.

    -Jim

Ian Fritz wrote:

> ----- Original Message -----
> From: "jh." <jhaible at t-online.de>
> To: "Ian Fritz" <ijfritz at earthlink.net>; <grichter at asapnet.net>;
> <synth-diy at dropmix.xs4all.nl>
> Sent: Sunday, September 09, 2001 6:54 PM
> Subject: Re: [sdiy] linearize OTA for VCF?
>
> > I wrote an email to National's Bob Pease recently, asking for the theory
> > behind the resistor-biased linearisation diodes of the 13700. The data
> > sheet speaks of current sources (as if it were the ordinary Gilbert
> method),
> > but as Jörgen Bergfors found out, replacing some of the resistors with
> > current sources destroys the 13700's linearity. With RAP's recent
> > articles on expo stuff, I thought I'd give it a try. Unfortunately, his
> > reply
> > was less than helpful. He spoke of an obsolete product, and basically
> > asked me to analyze the circuit myself. (;->)
>
> LOL! In other words, he doesn't know.
>
> Did he have a suggestion for a non-obsolete replacement?

--
 -Jim
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