@User while editing capacitor symbols to show the capacitance value based on W and L, i see the

cap_var_hvt

is not loaded in open_pdks spice models. if you see the file

.../share/pdk/sky130A/libs.tech/ngspice/all.spice

it loads:

.include "../../libs.ref/sky130_fd_pr/spice/sky130_fd_pr__cap_var_lvt.model.spice"

but does not load the

cap_var_hvt

high voltage capacitor, although that file exists in libs.ref (

sky130_fd_pr__cap_var_hvt.model.spice

). May be this capacitor is blacklisted /DNU for some reason? EDIT: Looking at the models these 2 capacitors have the same

tox

, so i believe there is no need to have both. the capacitance per area is indeed almost identical, and the

cap_var_lvt

has lower

vth

so behaves closer to an 'ideal' capacitor at low voltages, better than the

cap_var_hvt

These are varactors, so the MOS threshold voltage changes the voltage range over which the device goes from minimum to maximum capacitance. I already have a script in open_pdks that modifies

all.spice

to include missing devices. I didn't notice before that the HVT varactor was missing, but it is trivial to expand the script to add it. There are probably more missing devices in

all.spice

, so just let me know when you find one.