@User in skywater there are multiple models (multiple 'bins') depending on W/L, given a certain transistor geometry the closest bin is used for simulation. May be these different 'bins' have slightly different parameters.

@User I have used a sky130_fd_pr_nfet_01v8 and simulated the design using TT model.

In the file sky130_fd_pr__pfet_01v8__tt.pm3.spice there are 108 models: .model sky130_fd_pr__pfet_01v8__model.0 pmos .model sky130_fd_pr__pfet_01v8__model.1 pmos ... .model sky130_fd_pr__pfet_01v8__model.107 pmos Selection of the right models depends on the Lmin/Lmax / Wmin/Wmax for each bin.You might want to have a look. I don't know how the 'Kn' param is calculated from the model parameters.