Hello, I want to make a constant current LED driver circuit that runs at 700mA with an input voltage of 12V - 13.5V Is it alright to use the LM317 to build this? (got this from this thread http://forum.allaboutcircuits.com/showthread.php?t=57820) That would require the value of R1 to be 1.78 Ohms. The LM317 also needs a 3V drop to run. I found this other circuit (on Instructables) using a FET and a NPN BJT that looked pretty good and supposedly only needs a 0.5V drop to run. Any input on which would be more efficient and require a smaller heat sink? Thanks.