CONSTANT CURRENT SOURCE

Description In the following circuit an LED is used to give a fixed reference voltage to a transistor. The output constant current I out is given by: The LED lights up only when a load is connected at the output. Thus it indicates when the circuit is operating. The operation of the circuit can be made clearer by re-arranging the components as follows: The output will be limited to 100mA by using a red LED and 10R for Re. The output will be limited to 500mA by using a red LED and 2R2 for Re. The output will be limited to 1A by using a red LED and 1R0 for Re. Circuit Diagram