pspice
I tried to create a simple simulation in Orcad PSPICE. For some reasons, the measured AC voltage across the capacitor C is shifted -20 Vdc. Its value should vary in the range [-20V, +20V] as far as I'm concerned. Very appreciate if anyone can give me an idea of what's going on here. Thank you very much.
I imported the netlist into LTSpice and it worked ok (I only had to rename V(CL) to V(4) in the .PROBE directive, since LTSpice didn't recognize that syntax to specify the voltage across the cap):
The results of the simulation are shown below:
Therefore there is nothing inherently wrong with your netlist. Probably the simulation engine of PSPICE didn't succeed to find a solution for the equations. Try to fiddle with the simulation accuracy parameters (I don't use PSPICE, so I cannot help with that).
Although this is an old question. It would be worth noting that there are 3 things going wrong here. Firstly, ITOL should be lowered to be 1/10 of your lowest current, as well as IREL. This makes things take longer, but you need to have enough resolution for convergence. The biggest change should be to set the simulator to use the "Gear" method for convergence instead of trapezoid. What I believe that you have is something that is not converging with trapezoid due to resolution.
Best Answer
The initial charge of the capacitor is 0. You then start sucking out current through the current source (it starts with the negative cycle). The voltage can only decrease. Eventually the current source goes positive, the capacitor will get some charge again, and its voltage will increase back to the initial condition, 0 volt. Then the cycle repeats.