this is my first post in the site. Hope it's clear enough.

I need a 50mA current source despite the LOAD value, and I need the current flowing just when the microcontroller (uC) says so.

It works fine with LOAD=0ohm;IL=50mA, but when I enlarge the LOAD the current decreases (LOAD=330ohm;IL=11mA / LOAD=1,330ohm;IL=3mA).

What am I missing in the design?

^{simulate this circuit – Schematic created using CircuitLab}

Thanks a lot! Any thoughts will be highly appreciated.

I need a 50 mA current source despite the load value (resistor LOAD), and I need the current flowing just when the microcontroller says so.

It works fine with LOAD = 0 ohm and IL = 50 mA, but when I enlarge LOAD the current decreases (LOAD = 330 ohm and IL = 11 mA / LOAD = 1,330 ohm and IL = 3 mA).

What am I missing in the design?

^{simulate this circuit – Schematic created using CircuitLab}