[sdiy] SSM2164 Filter Cells

[Neil Johnson]

Hi,

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.

Neil
--
http://www.njohnson.co.uk