> Without details of the interface and WHY you think you need an OPTO,
> I can only guess... but you may just need  a power FET.
> (The small ones source/sink 1,000 mA.)

I'm using an OPTO because 1) I wanted to figure them out, 2) I need to use
them for another piece of this project (real noisy signal source) 3) I have
to make a 12v wave from a 5v wave.

The other piece of the project is the opposite - I need to take a 12v
hall-sensor output into my PIC and count the pulses. It all sorta smelled
like an OPTO opportunity.

-DO