I guess that people here are probably tired of LED questions, but I'll give these a shot anyway. 1) LED forward drops are specified over a smallish range, e.g.: 2.0 - 2.2V. Does this indicate a dynamic range, or is it that any one specimen of that type of LED will have a fixed drop somewhere in that range. 2) I want to drive a high brightness red LED @ 350mA from a 5V source, assuming a 2.2V forward drop across the LED. I calculate the current limiting resistor as 8R, power dissipation across it as ~1W. So far, so good (I hope :) ). The nearest preferred value resistor available is 8R2, but not many vendors carry 1W 8R2. So basically, the question is, what are my options beyond ordering the aforementioned resistor? I know that there are some ICs out there that do constant current, but I was wondering if there was anything I could do with good old 0.25W resistors to spread the power dissipation across multiple ones. 3) How critical is the current anyway? I know that 350mA is the recommended current, and that they will do 400mA pulsed. I plan on controlling the brightness via PWM switching, so how does, for example a 50% duty cycle affect the current through the LED. My guess would be that you get 50% at full current, then 50% at none - and that the off periods allow the LED to cool. This effectively cooler running means that you can drive it at 400mA in the on phase? Cheers, Chris.