>
> > I'm loooking for a two terminal constant current device that could be put
> > between an LED and a variable DC supply to hold the LED current at 5mA as
> > the supply varies over a 0-10V range (recognizing we're not going to get
> > it at 0V, but I'd like the widest range possible).

As you approach zero, the problems begin. In fact, with a red LED you'll
need at least 2V.
An LM317 regulator can be set as a constant current source, at a  penalty
of another couple volts.

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