AW: Transistor matching

[Joachim Verghese]

On Mon, 9 Dec 1996, Haible_Juergen#Tel2743 wrote:

> I had to select a few transistors recently, and I just used a
> bipolar 15V supply and two 150k resistors. Ok, 150k from
> 15V - Vbe is not an ideal current source, but two identical
> transistors should give the same Vbe at the same 150k
> resistors as well, no? Or did I miss something?

I think your method works ok, since you're *comparing* two devices.

Using a "real" current source is perhaps more scientific and
preferrable when you need absolute Vbe figures of your devices.
With this latter method, there's no interaction between Vbe and Ic,
Ic being held constant.

BTW, how's your VCA project advancing? :)

-joachim