[sdiy] Moog VCHPF pole's NPN/PNP matching

[Jarno Verhoeven]

BC847PN might be an option, not matched though, and SMT (AND pretty d*mn small).
Apparently matching NPN/PNP is always a problem. Even THAT corp do not specify
matching across PNP/NPN pairs in their THAT340.

Jarno.


> Op 22 april 2014 om 15:15 schreef Jean-Pierre Desrochers <jpdesroc at oricom.ca>:
> 
> 
> Did anybody build a Moog 904B VCHPF circuit?
> The schematic states that all the NPN/PNP pairs
> used in the 4 poles chain (Q13,14 Q17,18 Q21,22 Q25,26)
> needed to be matched pairs.
> See the circuit here:
> http://www.freeinfosociety.com/electronics/schemview.php?id=944
> 
> I read lots of threads on the list about this issue
> with no findings ..
> Well I matched a lot of NPN pairs (2N3904)
> and PNP pairs (2N3906) last weekend using Bob Moog's
> little matching setup with very good results
> (better than 2mv in matching values !) but I'm having
> a hard time to match NPN/PNP pairs in my lot..
> The 2N3904 batch are around .600v @ 100uA
> but the 2N3906 batch are around .650v @ 100uA.
> Anybody knows good complimentary pairs available
> or a way to compensate for the vbe differences ?
> I'm considering specialised NPN/PNP IC matched pair.
> 
> JP
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