I have a little LED flashlight which SEEMS to be using the internal resistance of the batteries to limit the current. It does not work if you use a power supply (I think it draws too much current), but on three series AAAs, it works fine. I'm not sure about the battery life, though. Sean On Feb 11, 2008 2:19 PM, David VanHorn wrote: > 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 > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist