Hi , I am trying to simulate the below spice file : --------------------------------------------------- **.subckt nmos_3v3 XM1 vds vgs GND GND sky130_fd_pr__nfet_03v3_nvt L=0.5 W=1 nf=1 ad='int((nf+1)/2) * W/nf * 0.29' as='int((nf+2)/2) * W/nf * 0.29' + pd='2*int((nf+1)/2) * (W/nf + 0.29)' ps='2*int((nf+2)/2) * (W/nf + 0.29)' nrd='0.29 / W' nrs='0.29 / W' + sa=0 sb=0 sd=0 mult=1 m=1 VDS vds GND 3.3 VGS vgs GND pwl 0n 0 10n 1.1 20n 2.2 30n 3.3 40n 4.4 .lib ./models/sky130.lib.spice tt .tran 0.01n 100n .save all **.ends .GLOBAL GND .end -------------------------------------------------- Now , since the VDS is constant to VDD and its a 3V3 NMOS , and sweeping the VGS from 0 to 3v3 , expecting to get the VTH for the nmos. But seems the IDS is linearly changing - any ideas whats going wrong ??