On Feb 11, 2008 1:53 PM, Richard Caldwell wrote: > Hi, I've always thought that LEDs drop 1.7 Volts due to the PN junction depletion layer. I have a Surefire torch with a really bright white LED and it takes two series 3volt batteries. Is this an LED with an internal PN junction that is somehow rated for 6v or is it an LED made of several series junctions? Can anyone explain? Vf on leds is related to the wavelength of the emitter. 6V in sounds like they are using a buck regulator in constant current mode to feed the led. My Inova lights are like that. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist