[sdiy] Fairchild uA726

[Mike Gorman]

Geoff,

The three that I received from utsource have a date code of 9850, so
hopefully they aren't parts from the eBay scam.

It will be a while before I can test them, but I've just had a look at the
Formant circuit and it should be possible to breadboard part of the Formant
Oscillator to see if these chips are working. I might give them a try next
week sometime.

Regards

Magman

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of geoff james
Sent: 24 September 2009 08:49
To: synth-diy
Subject: Fw: [sdiy] Fairchild uA726

Hi all , are these possibly the knock offs that were for sale on ebay.
The image they show seems to indicate they were manufactured in 2005.
Maybe not the real deal. Go look--www.utsource.net
Regards
Geoff
----- Original Message ----- 
From: "Carsten Tönsmann" <carsten at analog-monster.de>
To: "David G. Dixon" <dixon at interchange.ubc.ca>; 
<synth-diy at dropmix.xs4all.nl>
Sent: Thursday, September 24, 2009 2:09 PM
Subject: Re: [sdiy] Fairchild uA726


>
> The old Formant VCOs did.
>
> Carsten
>
> ----- Original Message ----- 
> From: "David G. Dixon" <dixon at interchange.ubc.ca>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, September 23, 2009 7:50 PM
> Subject: [sdiy] Fairchild uA726
>
>
>>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?
>>
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>
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