SRAM Cell Hold SNM
* Static Noise Margin

.lib "./libs/models/sky130.lib.spice" tt

*** Inverter 1
XM1 qbar1 q1 gnd gnd sky130_fd_pr__nfet_01v8 w=0.42 l=0.21
XM2 qbar1 q1 vdd vdd sky130_fd_pr__pfet_01v8 w=0.84 l=0.21

*** Inverter 2 
XM3 q2 qbar2 gnd gnd sky130_fd_pr__nfet_01v8 w=0.42 l=0.21
XM4 q2 qbar2 vdd vdd sky130_fd_pr__pfet_01v8 w=0.84 l=0.21

V1 vdd gnd dc 1.8V
V2 q1 gnd dc 1.8V
V3 qbar2 gnd dc 1.8V
.dc V2 0 1.8 0.01 V3 0 1.8 0.01
.control
run
plot V(qbar1) vs V(q1) V(qbar2) vs V(q2) 
.endc
.end