[sdiy] matched transistors

[Brown David]

There are several issues here.
1.  Obviously an integrated transistor pair such as the MAT02 will have
better thermal tracking than two separate transistors glued together.
2.  I'm not clear about which parameters are the most important for a
matched pair.  I had assumed a good Hfe (gain) match was all that matters.
However other contributors to the sdiy list has suggested matching Vbe to
within a millivolt or so is important.  Anyway, you test procedure sounds
OK.
3.  Where did you obtain the Format Pro book from?  Is it in English or
German?  I built (and am still completing) the original Formant.

I hope this email will appear on the sdiy list.  At the moment, I'm
receiving what other people have posted, but nothing I've sent.  I'll try
subscribing again!


-----Original Message-----
From: Terje Winther [mailto:terje.winther at notam02.no]
Sent: 04 February 2002 20:56
To: Brown David
Subject: RE: [sdiy] matched transistors


>For VCOs, the matching needs to be very close.  For example, the gains of
>MAT02 pair are advertised to be within 2%.

So far i have only used pair that are within 1% apart, but it takes forever
to measure a batch. If I could go to 2%, it would significantly reduce
preparation time.

>By the way, how are you measuring the transistor gains?

I really don´t know; I have a measuring instrument someone else have made;
I just insert them properly, let them be in there for quite a while (many
minutes each), note down the reported number and move on to the next.

I am planning to build a gain tester for some transistors needed in the
Formant Pro VCOs, based on what is detailed in the book.


tw.  :)

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