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Hello, I'm trying to design a modified Schmitt-triggered inverter using the Sky130 opensource pdk. I have calculated the inverter switching point needed for my design, the problem is that I couldn't simulate the hysteresis plot in ngspice. The VSPH of the n-type Schmitt with the ascending dc sweep works well, but the VSPL doesn't work when I try a decreasing dc sweep.
Here is the ngspice netlist:
Here is the ngspice netlist:
Code:
** sch_path: /foss/designs/test3.sch
**.subckt test3
XM2 VOUTN VIN VDD VDD sky130_fd_pr__pfet_01v8 L=0.15 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=3 m=3
XM1 VOUTN VIN net1 GND sky130_fd_pr__nfet_01v8 L=0.15 W=1.2 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=2 m=2
XM3 net1 VIN GND GND sky130_fd_pr__nfet_01v8 L=0.15 W=1.2 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=2 m=2
XM4 VDD VOUTN net1 GND sky130_fd_pr__nfet_01v8 L=0.15 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
VDD VDD GND 1.8
VIN VIN GND 0
**** begin user architecture code
.control
dc VIN 0 1.8 0.01
plot v(VOUTN) vs v(VIN)
reset
dc VIN 1.8 0 -0.01
plot v(VOUTN) vs v(VIN)
.endc
.save all
.lib /foss/pdks/sky130A/libs.tech/combined/sky130.lib.spice tt
**** end user architecture code
**.ends
.GLOBAL GND
.GLOBAL VDD
.end
