I tried it, but something went wrong, the value doesn't change correctly with the control voltage. with 10 ohm Rsense, it doesn't change at all.

You have the inputs of the TL081 at only 1V but they do not work if their voltage is less than 3V.
The inputs are supposed to be close to the positive supply voltage.

 

Oops, Thank you very much 'Audioguru' for pointing to this error. I changed the opamp.

Yehdev, the limitation is that you *can't* put more current through a resistor without a higher voltage drop.

The bottom line is that you must define your requirements...

* What is the maximum load resistance you want to test?
* What is the maximum current you want to test? (You said 100 mA.)

From those two things, you will be able to determine how high of a supply voltage you need, to be able to send that much current through a resistive load.

'Audioguru' and 'sage.radachowsky' .. I can't thank you enough for you help and your friendly advices. I much appreciate it.

You'll need the voltage to be enough to send through the load, plus a little more for the current sense resistor.

If you want to use a supply voltage higher than 5V, then yes, you can change the op amp to another one... and be sure to choose one with rail to rail inputs.

Or, you could also simply keep the 5V supply for this op amp and draw the load supply power from 12V or higher. That would work, too, because the sensing and control all works below 5V.

I added a simulation of that last solution.

Finally it worked in simulation with components I can find in my area... Thank you very much.
I used MC33078D opamp, with +12 volt supply.

 

Oops, didn't notice it's a current sink, trying to modify the circuit accordingly.