At 05:04 PM 6/24/2004 -0500, you wrote:

>> > 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.

If you go three terminal, and multiple components, it's not that hard to get
within some mV of the actual forward voltage, but kind of a pointless
design exercise..

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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