PNP arrays

Martin Czech martin.czech at intermetall.de
Tue Jan 26 09:29:12 CET 1999


I use the CA3096 for the expo converter in my version of the WASP filter
clone by J.H..  I know that the pnp are crap, but I hope that they work
for this application (the cicuit works, but I never checked tracking).

hfe of 40 is no good for an expo converter, but the hfe figure should
be better for lower currents. And I have thermal matching, and even on
chip heatimng by the three npn. So the hope is that this pnp pair will
be able to feed a ca3080 current source for my tri osc. in a reasonable
way, so that I get acceptable tracking in the lower octaves, where it
is more about leakage. I hope that a can "invent" some kind of tracking
adjust for the higher octaves, so that it will track there as well.

OTOH I want linear control as well (e.g. hard sync linear sweeps).
I guess I won't be able to adjust ecpo and linear tracking at the
same time.

So it would certainly be better to use a pnp-pair with more performance,
but the few parts that are on the market don't allow for chip heating...
and that means that the thermal error will be much worse then the scaling
error because of low hfe, we had just a mail about thermal results...


m.c.




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