[sdiy] Fairchild uA726

[Aaron Lanterman]

The original Buchla 258 used it, If I recall correctly, the modulation  
oscillator of the Music Easel uses it (but not the principle  
oscillator) I think of of the early Roland polys (Jupiter 4 maybe?)  
used them.

You pretty much have to design around them nowadays and replace  
anything with a 726 with some alternative expo converter.

- Aaron

Sent from my iPhone

On Sep 23, 2009, at 1:50 PM, "David G. Dixon"  
<dixon at interchange.ubc.ca> wrote:

> I was flipping through a fantastic (albeit very old: 1976) book I  
> found
> languishing in the stacks of the UBC library, the "Handbook of  
> Operational
> Amplifier Circuit Design" by Stout and Kaufman.  I was studying the
> schematic for "a differential-input logarithmic amplifier with  
> adjustable
> gain and logarithm base" in Fig. 17.1 on page 17-2, when I came upon  
> this
> passage:
>
> "Several other design tricks will keep this circuit from drifting with
> temperature.  Transistors Q1 and Q2 should be a matched pair of  
> devices on
> one chip.  Ideally they should be gain-regulated such as the uA726
> temperature-controlled differential pair (Fairchild).  This device has
> active temperature-regulating circuitry on the same chip as the  
> matched pair
> so that external temperature sources have no effect on transistor
> parameters."
>
> This sounds like the ideal device for building expo converters.   
> However, I
> could find no reference to it on Google, and no datasheet in the
> datasheetcatalog.com database.  Does anyone here know of this chip?   
> Is
> anything similar still being manufactured?  Did any vintage synths  
> use it?
>