PAiA VCO

[danial stocks]

>From: patchell <patchell at silcom.com>
>To: synth-diy at node12b53.a2000.nl
>Subject: Re: PAiA VCO
>Date: Mon, 07 Aug 2000 19:55:45 -0700
>MIME-Version: 1.0
>Received: from [24.132.43.83] by hotmail.com (3.2) with ESMTP id 
>MHotMailBB58C4190023D820F39C18842B5334B20; Mon Aug 07 20:06:07 2000

>     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.
>

Haven't had the chance to check out this cct I think I missed the URL 
somewhere, but one thing maybe shed some light is the linearize diode in the 
ota actually affects the gm with it's own current.. I saw this in a circuit 
for AGC using the linear diodes as controlling elements.Also noted the same 
when fiddling with something VCA a while back... so varying current thru the 
diode will most likely actually vary osc freq.
Cheers,
Dan

________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com