I want to make the laser (Iop < 20mA and Vop < 2.5V) blink with help of MicroController. I made the following circuit and tried to test it using a 10k resistor instead of the laser in order to check the current flowing through the drain of the transistor. So when I was measuring the voltage at the source of the transisor it was showing the 1.4V and wasn't change when a signal at the non-inverting pin changed.
When I disconnected the output of the OpAmp from the gate the voltage at the drain became 0.4V and the voltage at the output of the OpAmp was 2.7V in spite of voltage quantity of the signal pulse (V_pulse = 3.3 or 0).
What was wrong? Is there any mosfet transistor (dip type) that will fit better for my goal? Or do they only work with high current? Is there a circuit that is better than what I want to make?
UPD: Is the schematics from this answer apropriate how do i create a current source? There are no transistor at all