Many thanks. What I had been looking for was something like those 3-legged devices=20 seen in modern (cheap) LED flashlights. But something kept tickling=20 in my mind and it finally came to me - there has been much discussion=20 on this list regarding cheap but discrete switch-mode buck=20 regulators. So I went looking for those discussions. That lead me to Russell's GSR regulator and Richard Prosser's design=20 which lead to Roman Black's regulator. Configuring any of those to be a current regulator is dead simple and=20 the only drawback is the same issue that I have with the standard=20 2-transistor constant-current linear regulator: current varies with=20 temperature. But I can fix that if it turns into a problem. I'd still like to see if one of those little LED drivers might work=20 for me but I'm proceeding with a discrete regulator for now. At=20 least for the initial prototypes. Many thanks! dwayne At 11:23 AM 7/22/2014, Sergey Dryga wrote: >Dwayne Reid planet.eon.net> writes: > > > > 28Vdc max input voltage > > 10mA output current > > works down to -45C or colder > > readily available from North American distributors > > > >How about switching voltage regulator and resistor setting LED current? >E.g. https://www.dimensionengineering.com/products/de-swadj3. It has >acceptable Vin range, and good efficiency. > >Or you can use any of the switch mode power supply controller chips, and u= se >voltage on current sensing resistor for LED as a feedback. > >Hope this helps, > >Sergey Dryga --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .