[sdiy] SSM2164 Filter Cells

[David G. Dixon]

> > A resistor-to-ground
> > and follower should also work just fine if you don't want to invert,
> 
> I'm not sure about that with the 2164... I do recall reading something
> on the datasheet about its particular current output wanting to see a
> virtual ground in order to be happy (not the case with a usual OTA).

Yes, in the standard configuration, the datasheet suggests that "The output
current pin should be maintained at a virtual ground using an external
amplifier."  However, in the absolute maximum ratings, the input, output,
and voltage control pins can range from -V to +V.  Given that the Iout is
internally connected to a couple of transistor collectors, I can't see why
it would matter too much.  In any case, this might be worth doing some
breadboard testing.

Also, I misspoke before (it happens a lot with me): the impedance of the
control voltage pin is 5k.  7.5k is the resistor to use for class A/B
operation at the mode pin.