I'm trying to build an OpAmp based high constant current source/sink based on the analog devices application note 968.
In the first step I designed it for maximum of 1A, but later up to 10A is planed. The load with 1mOhm is just an example for very high load that should be restricted by this circuit.
Everything works as expected as long as the load voltage isn't pulsed (or even turned on once) in some way. In my example I added a load voltage source VL with 50Hz pulsed 20V to demonstrate this. To be precise: In case of a constant current source VL is the voltage source the circuit will provide to the load. In case of a current sink, VL is the voltage source the user will provide to sink into this circuit.
What happens is, that there is a large unrestricted peak current flowing through RL for about 20µs. After another 20µs the current stabilizes to the expected set current.
I tried to change C1 in various ways. Choosing too small values causes the OpAmp to swing like in following example. The lower C1 the larger are the swing peaks.
I played with various OpAmps and mosfets types but there were no real change. Is there a way to prevent this high peak current in some way? What could I change? Is this peak current really a problem since it's time is really small?