Can anyone explain to me how a constant current LED driver IC output circuit typically works? Basically I am trying to replicate some old (obsolete) LED driver ICs which have constant current outputs. I know that they aren't very "good" constant current sources, that they would be a simple as possible, etc, but I can't seem to find a schematic diagram anywhere. I could certainly do "good" constant current sources (with op-amps or bias transistors, etc) but I am looking to have them be as simple and small (and inexpensive) as possible-- they also need to be digitally switchable.
(p.s. I have looked into ICs that have them to use them as is, but I have yet to find a single satisfactory IC for that, so I am looking into discrete but simple designs.)
Thanks for any help!
