[sdiy] Temperature Compensated VCO attempt - help?

[Magnus Danielson]

From: patchell <patchell at silcom.com>
Subject: Re: [sdiy] Temperature Compensated VCO attempt - help?
Date: Sat, 01 Feb 2003 09:53:57 -0800

Dear Jim and Scott,

>     Very preliminary results...but I would say you have a winner here
> Scott.  I haven't reduced what little data I have yet, but the expo
> converter looks very stable.
> 
>     Scale conformity I am getting is pretty much as before, although, I
> haven't checked it over 8 octaves yet.  But over 5 octaves I am getting
> about +/- 2 cents (same as before, no big surprise).
> 
>     I need to get a few more points before I can calculate the tempco.

Sounds good, but I still haven't got a comment on the possibility of a
diffrential drive error of the OTA. Am I the only one seeing it or?

Is it that my derivations deviates from your in some fundamental way?
The single sided input will contribute to both the diffrential mode and common
mode of the OTA input, where the output of the OTA is Iabc*Idiff/Icommon.
You would get a scale error if you feed into both the diffrential and common
mode input currents, right?

BTW. I did the full linearized OTA derivation, but using a different
linearization model, but it should not do any major thing other than switch a
few signs.

Cheers,
Magnus