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

[Jean-Pierre Desrochers]

Hi  Carlos,
> I dont think you need to match the NPN with PNP for this filter. Only
> pnp with pnp and npn with npn.

If you look carefully at the right bottom
of the schematic:
http://www.freeinfosociety.com/electronics/schemview.php?id=944

You will see (Q13,14 Q17,18 Q21,22 Q25,26) are 4 matched set.

JP

Le 2014-04-22 11:22, Carlos Portela a écrit :
> I dont think you need to match the NPN with PNP for this filter. Only
> pnp with pnp and npn with npn.
>  If you need to match npn with pnp try to buy more from different
> sources.
> 
> C
> 
> 2014-04-22 16:44 GMT+02:00 Jarno Verhoeven <jarno.verhoeven at ziggo.nl>:
> 
>> 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
>> [1]
>>> 
>>> 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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> 
> 
> 
> Links:
> ------
> [1] http://www.freeinfosociety.com/electronics/schemview.php?id=944
> [2] http://dropmix.xs4all.nl/mailman/listinfo/synth-diy