[sdiy] linearize OTA for VCF?

[Ian Fritz]

----- 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?