Archive for August, 2012

LED Dimmer using Current Mirror

The circuit below is a straight forward way to provide continuous control over the intensity of one or more LEDs using a current regulator circuit based on a crude current mirror.

Linear LED Intensity Controller

Linear Regulator LED Intensity Controller

Summary

  • Q1 buffers the potentiometer voltage a little.
  • Size R2 for maximum current through the LEDs.
  • Q3 “mirrors” the current pushed through Q2 despite the voltage drop of the LED string.
  • The compliance range of Q3 is the battery voltage less about 1V.
  • R3 and R4 are optional, but improve the balance of the mirror by reducing the variability of emitter resistance.