Matchin transistors

[Joachim Verghese]

On Fri, 13 Sep 1996 johns at oei.com wrote:

>      But are you saying that the term "matched transistors" really 
>      indicates 2 transistors in good thermal "sync" (using come good 
>      thermal coupling) rather than 2 transistors selected for closely 
>      matched VI and gain characteristics?

No. "Matched transistors" implicitly means that the devices have
closely matched Vbe-Ic characteristics. (And in order to maintain
matching over a range of temperatures, the devices need to be
thermally coupled, too).

This, I assume, is because that's what's needed to build good
differential amplifiers and current mirrors - two of the most popular
and useful transistor applications.

The exponential converter is a totally different application,
and therefore the matching requirements differ too.

-joachim