[sdiy] Fairchild uA726

[Oren Leavitt]

David G. Dixon 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?
> 

Hi David,
Yes, there has been lots of uA726 discussion on the list in the  past.
Check out the SynthDIY archives here:

http://search.retrosynth.com/synth-diy/

Plunk "uA726" into the search box.
The 726 has been used in some vintage synths, and the old "Formant" 
modular synth project from the period.

- Oren