30-mA LED Dimmer

If you’ve ever tried dimming a LED with a simple potentiometer, you know that the approach does not work very well. Just as with ordinary diodes, the voltage-current characteristic of LEDs is far from linear. The result — depending on the potentiometer setting the LED brightness will hardly change most of the time as the pot is turned and a sudden variation at the end.The best method to tackle this problem is to power the LED from a current source with zero to 100% adjustment range. The circuit shown here is an example.