Transistor matching method ?

Don Tillman don at
Thu Jan 25 17:47:58 CET 1996

   From: Haible_Juergen
   Date: Wed, 24 Jan 96 12:30:00 PST

   > for testing the BC109s, and I seem to recall that I matched them
   > (for Vbe, not for hfe). The whole thing was hastily built on copper

   When I built the Moog filter, I used the Vbe matching method suggested
   by Moog. But now I often just use my multimeter to match hfe's when I
   need a pair. I really don't know if that makes sense at all. I'm quite
   sure that it's not the same, but the parameters would be dependant on
   each other somehow ... anyone who can tell me exactly?

Vbe and Hfe may be somewhat related, but not closely.  In a project
like this the Vbe value is important and the Hfe value is mostly
irrelevant, it doesn't make sense to match on the wrong parameter.

(I'd even go one step further and match them with as many parameters
as possible setup to the same values that the transistors will see in
the actual circuit.  Vcb for instance.)

  -- Don

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