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

[Andrew Simper]

J P I wouldn't sweat the matching too much of those transistors, just
bother with the ones marked with (M). Mismatch in the other ones with
change the cutoff (and non-linearity) slightly as the current will be
slightly different being push / pulled between capacitors, but the
capacitors will most likely have way more mismatch than the
transistors, so they should be the first things you should match (C5
C6 C7 C8 0.39 uF).

I've done some tests with BC550 NPN vs 0.47 uF poly caps and the
maximum error between the most mismatched transistors was around 0.35%
, but the maximum error between the caps was 4% !!!

-- Andy


On 23 April 2014 09:25, Michael E Caloroso <mec.forumreader at gmail.com> wrote:
> According to my vintage Fairchild databook, the 2N3096 (PNP) has the
> same hfe spec (aka gain curve) as 2N3094 (NPN)
>
> You are correct about matching NPNs to NPNs for the HPF.
>
> MC
>
>> I don't think you have to match the PNPs and NPNs gain wise. Think you just
>> have to match NPNs to NPNs and PNPs to PNPs. 2N3904s and 2N3906s don't have
>> complementary gain curves so that will be hard to do anyways.
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