to continue my comment above, the schematic is enclosed. Trying to use pfet_01v8_lvt. spice says the following. as I mentioned -- using only the nfet version does not seem to cause any problem for spice. library command is" .lib /usr/local/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice tt"

Looking at the PDK for pfet_01v8_lvt, it appears that the minimum Lg is 0.35um.

David, I was using the default values in the pfet symbol to learn the tools/toolchain so I didn't give any thought to the L/W parameters. You are absolutely right, changing the length of the pfet from 0.15 to 0.35 made the simulation work fine. THANKS SO MUCH FOR YOUR HELP!!!!