LED Driver problem

Yup... that LM 3914 looks like the one I've used before. NS usually have V good app' notes.

Del

LED's need about 1500mV minimum before they emit light. Are you asking whether or not you can modify the LM 3914 circuit to make it work from zero to 1500mV with no higher voltage available? The LM3914 is actually a bunch of comparators and a voltage divider. The LED's are virtually driven digitally from a higher source voltage, and the external resistor deterrmines how much current flows through the LED's, which inherently controls brightness.

Hook up an LED to a variable power supply, and slowly raise the voltage from zero until you just begin to see light. Don't raise it much higher, or you'll destroy it. You must reach that threshold voltage before the LED becomes forward biased and starts emitting light. I think you'll get a good handle on what I'm talking about.