[sdiy] LM394 vs. MAT02 vs. ?

[Scott Stites]

Rene's VCO4069 uses an NPN/PNP pair.  But, maybe was inspired by the ARP design? =0)  In any event, it does deliver an expo response.  


Cheers,
Scott


-----Original Message-----
From: Metrophage <c0r3dump23 at yahoo.com>
Sent: Nov 8, 2004 8:14 AM
To: Glen <mclilith at charter.net>
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] LM394 vs. MAT02 vs. ?

--- Glen <mclilith at charter.net> wrote:

> At 11:24 AM 11/5/04 , Roy J. Tellason wrote: 
> >> The ARP VCOs I have seen (and heard) used a weird PNP/NPN pair.
> >Yeah,  they used either 2N3904/2N3906 or TZ81/TZ581.

> I didn't know that 2N3904/2N3906 was an odd match. Aren't those parts
> used together all the time?
> 
> thanks,
> Glen

In the same circuit, yes, of course. But in an expo converter for a
VCO? I usually see matched NPNs used for sawtooth VCOs, and PNPs used
for triangle VCOs. A "pair" consisting of one NPN plus one PNP is what
is weird, at least, I don't know of other VCOs which use converters
like this. I wonder whether or not it really is all that "exponential"!
The ARP VCOs are rumored to be quite stable, but I'd have to wonder
about the scale and tracking.

CJ


		
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