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.
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.