[sdiy] Humans are not Becoming Smaller

[laxt57 at aol.com]

 Hi Ian
 My thought process was to reproduce something functionally like
 the 3080 to keep alive such designs as the  asm-1s and others.
 Pinout, footprint, and function as a drop in replacement.
 Jeri
-----Original Message-----
From: Ian Fritz <ijfritz at earthlink.net>
To: laxt57 at aol.com; synth-diy at dropmix.xs4all.nl
Sent: Fri, 03 Jun 2005 09:45:13 -0600
Subject: Re: [sdiy] Humans are not Becoming Smaller


At 12:47 PM 6/2/05, laxt57 at aol.com wrote: 
 
> Well what I am planning is this. A OTA made with SMD that 
> will fit the footprint of a ca3080. By input I guess I was not 
> asking about the design of the OTA itself, all that is freely 
> available on the web. I guess my question is with the available 
> smd devices 847s,3904 etc do you think this sdiy do able? 
 
Well, that's the question. I haven't found any good SMD well-matched, high-gain transistors. I've been stocking up on the popular Japanese matched pairs, some of which are quite good, but all discontinued. In my most recent discrete OTA I tried a pair of hand-matched ZTX795A's glued together, but they didn't work very well. They had too much LF noise, presumably due to temperature fluctuations. 
 
Maybe some of the non-monolithic SDMs could be made to work, I dunno. 
 
Another question is whether it is even a good idea to try to reproduce the 3080. The Iabc mirror has always been a pain, requiring a mirror in the expo converter. Why not work with the simpler discrete designs that don't have this "feature". 
 
  Ian 
 
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