[Al Skierkiewicz]

Micah,
The luminous intensity of an LED is a function of the current flowing through it. With a simple current limiting resistor, the intensity will vary with voltage supplied. In a constant current source, the current will remain the same with a varying supply voltage. Don't know if this is important for your application but I thought I would throw it in anyway. One place this was used in equipment I worked on is an audio console. This particular design used several LEDs for signalling which options had been selected. By wiring several LEDs in series and using a current source, the switches merely shorted across the LEDs that were not needed. The current source then kept the current constant and the LEDs were the same intensity whether one, two or all seven were on.