AW: How do I hand match transistors?

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Wed Feb 28 04:15:00 CET 1996


>
>I was hoping that someone out here in DIY land could take a moment to 
explain
>-
>in detail - how one goes about matching transistors by hand. Like how do I
>hook
>them up and what do I measure? - I need to match PNP's for use in exp.
>current
>sources. I know how to use a multimeter and all, but I'm not too keen on 
the
>properties of transistors.

Not difficult - You just need some patience.
Build a current source of about 100uA (I guess a 150k resistor from +15V
will do!). Connect the emitter to the current source, the base to GND, and
the collector to some negative voltage; maybe to -15V over a 120k Resistor.
Then connect a voltmeter between the emitter and base.
(connect the transistors to test over a socket of course)

Now comes the problem: As the be voltage is quite temperature sensitive,
you have to either
(1) wait until each transistor has cooled down from the warmth of your 
fingertips
      to room temperature again, or
(2) use thermally insulated tweezers, or
(3) heat your room to 37oC (;->)

JH.



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