[sdiy] SSM2164 Filter Cells

[David G. Dixon]

Neil, that specification blew right by me, and I didn't really understand
what it meant.  Thanks for clarifying.  I've always wired up 2164s exactly
as shown in the datasheet anyway, but it's always good to eliminate little
bits of ones ignorance when given the opportunity.

> David G. Dixon wrote:
> > 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.
> 
> The abs.max are simply what the device *should* be able to withstand and
> then recover from, but not necessarily what its normal operating region
> in.  Step outside the abs.max and you get blue smoke.  Go with what the
> datasheet states on the second page in the specifications table.
> 
> On the issue of the output transistors, note that the emitters of Q5-Q8
> sit at around 1.2V (assuming PN drop around 0.6V).  So there is no way the
> output pin can go above 1.2V, or anywhere near it.  If you allow a 1V drop
> across E-C then the output compliance looks realistic.