[sdiy] Speaking of OTAs/Matched Pairs????

[Jim Patchell]

    To match individual transistors, you need to build a transistor matching
circuit.  This is the one I did:

http://www.oldcrows.net/~patchell/matcher/matcher.html

    Somewhere on the internet there is the Bob Moog Circuit.

    Please note that the one on the above page is for PNP, you would need to
change the polarity of the power supply for NPN.  I measure the Vbe at two
currents, I just have a little toggle switch to do that job.  When matching
the transistors, you want to avoid handling them with your fingers (because
you will warm them up).  Also, try to do this while the temperature is not
changing much.

    So, all you do is set up the circuit, and measure the Vbe with a volt
meter (4 1/2 digit recomended).  I write down the two Vbe's on a piece of
paper and tape the transistor to that spot.  When I am all done, I start
matching up pairs.  I use epoxy to glue the two parts together.

    -Jim

ElmacacoX at aol.com wrote:

> ok, I'm following this matching thing, but I need a very simple question
> answered.
> my dmm has slots to test transistors, I've never done it, but is this what
> you guys mean by matching, measuring it with this?
>
>  a simple yes or no will do, since I know this can get complicated.
>
> thanks for helping a newbie,
>
> ed