I have been working on an analog multiplexer using discrete NMOS and PMOS devices. I have the gates connected to their respective sources through resistors and their drains are connected together. Positive and negative voltages are applied from source to source through a series load resistor. The NMOS works as expected - the body diode conducts when a negative voltage is applied and it blocks for positive voltage. But the PMOS device conducts when it should block. Here is the ASCII file for a simple test that shows this odd behavior.
A screen shot of the simulation:
I have tried this with several models of the PMOS device. I also closed and re-opened LTSpice. Am I not understanding PMOS devices or is something strange going on?
Thanks,
Paul