Can anyone design a programmable current source giving an output of 3A without using IC’s? Use only op amp, resistors etc

 

An opamp is an integrated circuit.

What do you mean by programmable?

What is the supply voltage?

 

An opamp is an integrated circuit.

What do you mean by programmable?

What is the supply voltage?

 

Something like this

 

sinking or sourcing?

 

Sinking

 

You are most of the way there. The drawing has the equation to determine the operating range of the circuit.

The drawing needs to be larger and more clearly readable. What is the input control voltage range?

Some things:

The TIP120 series of power transistors are Darlingtons.

There is no need for a base resistor.

Be sure to add decoupling capacitors to the opamp power pins.

How fast must the output respond to changes in the input?

The TL081 common mode input voltage range does not include the device negative rail. If you want the output current to be adjustable down to near zero mA, this opamp will not work.

ak

 

This looks an awful lot like a homework assignment? Is it?