Praveen Sundar

Thanks Holger, glad it checks out. I'll try a longer optran run like you suggest and open a separate ticket for it, with a small circuit that shows the problem. One more thing. While chasing the pswitch bug I put together a small checker that compares the AC result with the slope of the DC solution, and ran it over the other XSPICE analog models and the common built-in devices. It turned up 14 more bugs, where the AC matrix doesn't match the DC behaviour, for example: the native S/W switch loses...

Thanks for confirming it @h_vogt. I've attached a patch against current master (a80f6e3e). The problem is in the AC branch of the pswitch code model. Its conductance entries use the opposite sign to the DC current Jacobian, and it never stamps the control port's input loading. While checking that, I also found that the derivative in the logarithmic transition region wasn't normalized by the control voltage span, and that the control derivative stays nonzero where the resistance is clamped. aswitch...

PSpice VSWITCH (XSPICE pswitch) gives impossible AC gain (~4.6e15) in a passive divider, ps/ltps mode