My question might sound trivial. But I am playing around with CMOS Inverter with sky130 pdk with Ngspice. When I had len=0.15um, and Wp=3*Wn, my inverter threshold was close to Vdd/w. Now I changed the len to 0.3um, and now I need my Wp=30*Wn!!!! Any reason for this huge jump?

Don't know if this is relevant, but watch your units. I think the sky130 pdk spice models are scaled so that l=0.15 means 0.15um. l=0.15um would mean 0.15pm.

I have it set as l=0.15, I just mentioned 0.15um here for clarity.