PAiA VCO

Ian Fritz ijfritz at earthlink.net
Tue Aug 8 16:16:24 CEST 2000


Hi Jim --

Yes, this is all very curious. I hope to find time to wire this thing up and
measure its temperature dependence. I notice there is no drift spec listed.

  Ian

----- Original Message -----
From: "patchell" <patchell at silcom.com>
To: <synth-diy at node12b53.a2000.nl>
Sent: Monday, August 07, 2000 8:55 PM
Subject: Re: PAiA VCO


>     I just took a good look at the circuit.  I also redrew it , which I
find
> helps a bit.  But after I looked at it I saw something else that I find
> curious.  In the FAQ it said it was using the diode in the linearizer for
a
> temp sensor.  I don't think so.  In order to use a diode as a temp sensor,
you
> need to maintain a constant current through it.  The way the circuit is
set
> up, very little if any current will be flowing through that diode.  In my
> opinion, the tempco would be generated by the temperature dependence of Gm
of
> the transconductance amplifier.  Even if the diode were forward biased,
it's
> tempco would be canceled out the tempco of the Gm.  I depend on this for
my
> own electronically compensated exponential converter.
>
>     Time to break out the superstrip, I guess.  I am going to get to the
> bottom of this puzzel.
>





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