[sdiy] uA726 transistor array

[Magnus Danielson]

From: Takuya KATAYAMA <cxh02175 at nifty.com>
Subject: Re: [sdiy] uA726 transistor array
Date: Sat, 12 Oct 2002 21:53:44 +0900

Hi Takuya, Mike and others!

> Hello Mike and the List!
> 
> I cant recommend two individual Tr's instead of uA726.
> uA726 is a matched MONOLITHIC pair Tr's with controlled heater.
> 
> If you need pin-for-pin compatible replacement, uA726 had already
> obsoleted, you know.
> Instead of uA726, we make some feedback control circuit with TR array
> such as CA(LM)3046.
> It is very steadly and work well.

Well, yes. Out dear listmaintainer has an example on his webpage on how to do
this.

I've looked at the detailed schematic for the uA726 and it is possible to
acheive the same functionality. Weither the CA3046 has good enought properties
on the actual transistor parameters to match the transitors in the uA726 is
however one objection I recall for that setup. There is an issue about which
transitors really have to be tightly connected together thermally. The uA726
layout is quite ingenious and use more than the 5 transistors in the CA3046 to
operate. While a direct clone might not be the best road to pass, then the
question comes up if one can make another setup wich comes near or outperforms
the uA726. One of the benefits is the trimable temperature, linear and fast
control and overcurrent protection.

However, the aspect of thermal connectivity such as in the uA726 probably calls
for at least a few transitors to reside on the same chip.

Cheers,
Magnus