[sdiy] Analog MAT12 matched NPN pairs

Jay Schwichtenberg jays at aracnet.com
Sun Jun 1 21:54:32 CEST 2014


These are a lot cheaper and will work.

http://synthcube.com/cart/index.php?route=product/product&path=74_18&product
_id=162

There has been a lot of talk about how regular transistors matched are good
enough. I can see that for filters but I'm wondering about for VCOs. One of
the parameters that isn't mentioned anymore is rBE which can cause errors in
the exponential converter. This is mentioned in Electro Notes and on Rene
Schmitz's web site (http://www.schmitzbits.de/expo_tutorial/index.html). At
one point this was one of the reasons the expensive transistor arrays were
used. Rene's web site mentions that this can be compensated for if high
frequency trimming is put into the exponential converter. But still having
to trim something out seems wrong if you can avoid it. Also maybe picking
transistors that have a low rBE (which typically is NOT speced for a
transistor) would be better than the old 2NXXXX and BCXXX standbys.

Comments/discussion?

Thanks for the bandwidth.
Jay S.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of john slee
Sent: Saturday, May 31, 2014 6:48 PM
To: Synth DIY
Subject: [sdiy] Analog MAT12 matched NPN pairs

I think my MFOS modular PCBs arrived at work last week. I was
originally planning to match 2n3904s and cuddle them up in goo
and heatshrink, but these caught my eye as I was browsing Mouser
for VCO parts...

http://www.mouser.com/ds/2/609/MAT12-246314.pdf

Comments? They're quite expensive ($30+ each even in /10 qty)
but OTOH I don't need that many, and they're in nice shiny metal
cans, they're available, and they're already matched. Worth it?

John
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