# LED Constant Current Source Circuit Diagrams

Layout LED Constant Current Source
A simple LED can be used to stabilize the current in a circuit. A transistor and a LED function together as a stable current source. Circuit 1 shown in diagram 67.0 is the simplest version. T1 works as the on-off switch of the LED current source.

LED Constant Current Source Circuit Diagram |

### LED Constant Current Source

Circuit 1 shown in diagram 67.0 is the simplest version. T1 works as the on-off switch of the LED current source.

Circuit 2 shown in diagram 67.1 is an improved version by adding an extra transistor.

The constant current delivered by the circuit can be found mathematically by: Current (I) = 0.6V/R1