@Stefan Schippers - my spice file looks like below : ** sch_path: /home/ratul619/IIT_study_VM/xschem/sim_1t1r_IrefRcell.sch **.subckt sim_1t1r_IrefRcell R1 BL net1 5k m=1 XM1 net1 WL GND GND sky130_fd_pr__nfet_g5v0d10v5 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 C1 GND GND 1p m=1 V1 WL GND 3.3 V2 BL GND 0.2 **.ends parameter sweep * resistive divider, R1 swept from start_r to stop_r * replaces .STEP R1 1k 10k 1k * chapter 16.13.4.2 R1 1 2 1k .control let start_r = 1k let stop_r = 10k let delta_r = 1k let r_act = start_r * loop while r_act le stop_r alter r1 r_act run write dc-sweep.out v(2) set appendwrite let r_act = r_act + delta_r end *plot dc1.v(2) dc2.v(2) dc3.v(2) dc4.v(2) dc5.v(2) *+ dc6.v(2) dc7.v(2) dc8.v(2) dc9.v(2) dc10.v(2) .endc .tran 0.01n 100n .save all .option savecurrents .GLOBAL GND .end But ngspice is saying "parameter sweep - model name not found" Now i tried to integrate the function into my spice file. The standalone function may seen working fine