[sdiy] Matched transistors and EFM circuits?

[dj hohum]

I can't recall the details, but, it's in the archives. You pretty much
only need a multimeter.

On 6/11/07, gino wong <wonggster at gmail.com> wrote:
> 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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