I am trying to integrate the output of a Rogowski coil , with an inverting integrator with a reset circuit. I want to have the voltage level 0V during the off time of my switch, however after reset interval, the output voltage does not stay at zero and drops to some negative value.
EDIT 1:As per the answer by Spehro Pehfany, the problem indeed was the charge injection due to the JFET. However, I do not get the same problem with a non-inverting integrator, what might be the reason for that. I used the same device there too.