Opamp Constant Current Source Design

Opamp Constant Current Source Design

In This blog I will explain constant current source design using operational Amplifier. The explanation is also available in Video link given below in the blog.

Above is the basic circuit diagram of constant current using opamp. Due to virtual ground concept voltage at inverting terminal is zero. Current flowing through inverting terminal is zero because input terminal of opamp is very high.

Assume :

Ii = Current flowing the resistance R1 = Input current

IL= Current flowing through Variable resistance R3 = Load Current


Since No current will flow through opamp inverting terminal and hence

Ii = IL

Ii = Vin/R1

and hence IL = Vin/R1

So if Vin and R1 is fixed Ii remained constant even if load R3 changes. In spite of changing the load R3 the Ii remained constant. 

Application :

Opamp constant current source is used in LED droving as per below circuit.



The complete explanation can be seen in below video:

Thanks !!!


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