I'm giving it exactly 5 volts directly from a DC Power Supply and the output voltage should be 3.3V but it's not. I don't even have anything connected to the output pin of the regulator (holding it in my hand). It seems if V_in < 1.5V, V_out = about 0 plus a couple millivolts V_in >= 1.5V, V_out = V_in minus a couple millivolts I am using an http://www.national.com/mpf/LM/LM3940.html [Broken]. I've tried one from a box of them just to be sure I hadn't shorted the old one out. There's only 3 pins: V_in, Ground, and V_out....how can you mess that up? [/PLAIN] [Broken] I don't know what I am doing wrong as I am using some 7805s in my circuit which have no problem taking my 8volt DC and putting out 5volts. Any suggestions? Thanks.