[sdiy] Matched transistors and EFM circuits?

[gino wong]

In the past I had a friend with a machine that matched transistors for
me.  He moved and I now have bag and bags of small signal transistors
to match.  I have a Tektronics scope, a Simpson analog and a a Fluke
digital meter and a Hickpck 6000a tube trans checker.  What is the
best method to match transistors given these tools ?

best

gw

On 6/11/07, René Schmitz <uzs159 at uni-bonn.de> wrote:
> Hi Ian and List,
>
> Ian Fritz wrote:
> > At 08:00 AM 6/10/2007, Paul Schreiber wrote:
> >
> >>> Further, although I'm
> >>> aware that matching transistors in an expo converter is important for
> >>> temperature stability,
> >>
> >>
> >> Errr....nope.
> >
> >
> > Err ... yep.
> >
> > The transistors in an expo converter need to be matched so as to cancel
> > the Is prefactor.
> >
> > Late night?
>
>
> Well, it all comes down to the argument we had before. Let me recap real
> quick:
>
> Does Is1/Is2 give a constant or not. If yes, then Is1/Is2 does not
> really have to be unity. I.e. a mismatch could be tolerable without
> affecting the stability. In that case a mismatch could be due to
> geometry. (still good thermal coupling assumed)
>
> Your argument was always that there could be defects with could prevent
> Is1/Is2 to be a constant. However I still haven't seen a proof for that.
>
> I personally take it that there have been VCOs in the past, even in
> quite prominent gear like Minimoog, Oberheim SEM etc., which were using
> humble 3046s, as a hint that this whole matching issue isn't as
> important as some people would like to believe. It worked for them back
> then so why even spending the time to worry about it. :-)
>
> Cheers,
>   René
>
> --
> uzs159 at uni-bonn.de
> http://www.uni-bonn.de/~uzs159
>
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