* SPICE netlist
VD1 d1 0 {VDS}
VG1 g1 0 {VGS} AC 1
M1 d1 g1 0 b1 CMOSN l={L} w={W}
VB1 b1 0 {VBS}
VD2 d2 0 {VDS}
VG2 g2 0 {VGS+1m}
VB2 b2 0 {VBS}
M2 d2 g2 0 b2 CMOSN l={L} w={W}
V1 WL 0 {W_L}
B1 GM 0 V=(I(VD1)-I(VD2))*1000
.OP
+VERSION = 3.1 TNOM = 27 TOX = 5.7E-9
+XJ = 1E-7 NCH = 2.3549E17 VTH0 = 0.373994
+K1 = 0.4758551 K2 = 1.66382E-4 K3 = 1E-3
+K3B = 2.5522254 W0 = 1E-7 NLX = 1.751003E-7
+DVT0W = 0 DVT1W = 0 DVT2W = 0
+DVT0 = 0.4716151 DVT1 = 0.4314352 DVT2 = -0.348502
+U0 = 302.8182188 UA = -1.253128E-9 UB = 2.54065E-18
+UC = 5.025031E-11 VSAT = 1.103778E5 A0 = 1.8206564
+AGS = 0.3387292 B0 = -1.978357E-8 B1 = -4.001074E-8
+KETA = -8.550217E-3 A1 = 2.533352E-4 A2 = 0.6097524
+RDSW = 200 PRWG = 0.1248346 PRWB = 0.2
+WR = 1 WINT = 0 LINT = 0
+XL = 0 XW = -4E-8 DWG = -1.720799E-8
+DWB = 5.809278E-9 VOFF = -0.1001286 NFACTOR = 1.2811561
+CIT = 0 CDSC = 2.4E-4 CDSCD = 0
+CDSCB = 0 ETA0 = 4.939982E-3 ETAB = 3.203948E-4
+DSUB = 0.0242302 PCLM = 1.6958726 PDIBLC1 = 1
+PDIBLC2 = 2.522033E-3 PDIBLCB = 0.0473986 DROUT = 1
+PSCBE1 = 6.384899E8 PSCBE2 = 9.344316E-5 PVAG = 0
+DELTA = 0.01 RSH = 4.1 MOBMOD = 1
+PRT = 0 UTE = -1.5 KT1 = -0.11
+KT1L = 0 KT2 = 0.022 UA1 = 4.31E-9
+UB1 = -7.61E-18 UC1 = -5.6E-11 AT = 3.3E4
+WL = 0 WLN = 1 WW = 0
+WWN = 1 WWL = 0 LL = 0
+LLN = 1 LW = 0 LWN = 1
+LWL = 0 CAPMOD = 2 XPART = 0.5
+CGDO = 5.66E-10 CGSO = 5.66E-10 CGBO = 1E-12
+CJ = 1.742882E-3 PB = 0.99 MJ = 0.4674949
+CJSW = 4.033464E-10 PBSW = 0.9561194 MJSW = 0.340823
+CJSWG = 3.29E-10 PBSWG = 0.9561194 MJSWG = 0.340823
+CF = 0 PVTH0 = -7.086259E-3 PRDSW = -10
+PK2 = 3.582539E-3 WKETA = 9.966699E-3 LKETA = -3.974378E-3 )
.param VGS=0.9
.param VDS=1.8
.param VBS=0
+VERSION = 3.1 TNOM = 27 TOX = 5.7E-9
+XJ = 1E-7 NCH = 4.1589E17 VTH0 = -0.5627442
+K1 = 0.6417352 K2 = -1.640732E-3 K3 = 0
+K3B = 10.9622509 W0 = 1.003165E-6 NLX = 1.299543E-8
+DVT0W = 0 DVT1W = 0 DVT2W = 0
+DVT0 = 2.0159212 DVT1 = 0.8273532 DVT2 = -0.1747999
+U0 = 105.1311623 UA = 1.172379E-9 UB = 1.975361E-21
+UC = -1E-10 VSAT = 1.666411E5 A0 = 1.0602271
+AGS = 0.1915192 B0 = 9.931253E-7 B1 = 5E-6
+KETA = 9.224063E-3 A1 = 0.0245399 A2 = 0.300003
+RDSW = 1.741568E3 PRWG = -1.920108E-4 PRWB = -0.1424819
+WR = 1 WINT = 0 LINT = 2.982613E-8
+XL = 0 XW = -4E-8 DWG = -3.79137E-8
+DWB = 4.684167E-9 VOFF = -0.1400017 NFACTOR = 0.9786918
+CIT = 0 CDSC = 2.4E-4 CDSCD = 0
+CDSCB = 0 ETA0 = 0.4880906 ETAB = -0.0915552
+DSUB = 1.3195422 PCLM = 1.2495664 PDIBLC1 = 5.370494E-3
+PDIBLC2 = 1.344505E-10 PDIBLCB = -8.519944E-4 DROUT = 0.0685277
+PSCBE1 = 1.448131E10 PSCBE2 = 3.262949E-9 PVAG = 5.356024E-3
+DELTA = 0.01 RSH = 3.1 MOBMOD = 1
+PRT = 0 UTE = -1.5 KT1 = -0.11
+KT1L = 0 KT2 = 0.022 UA1 = 4.31E-9
+UB1 = -7.61E-18 UC1 = -5.6E-11 AT = 3.3E4
+WL = 0 WLN = 1 WW = 0
+WWN = 1 WWL = 0 LL = 0
+LLN = 1 LW = 0 LWN = 1
+LWL = 0 CAPMOD = 2 XPART = 0.5
+CGDO = 6.75E-10 CGSO = 6.75E-10 CGBO = 1E-12
+CJ = 1.893734E-3 PB = 0.9889579 MJ = 0.4705132
+CJSW = 3.124347E-10 PBSW = 0.8 MJSW = 0.2786992
+CJSWG = 2.5E-10 PBSWG = 0.8 MJSWG = 0.2786992
+CF = 0 PVTH0 = 4.757742E-3 PRDSW = -0.4256715
+PK2 = 2.63549E-3 WKETA = 0.028566 LKETA = -7.947746E-3 )
.param W=W_L*1u
.param L=0.25u
.step PARAM W_L 1 10 .1

* LTspice schematic (.asc)
Version 4
SHEET 1 528 896
WIRE 200 -448 -88 -448
WIRE 264 -448 200 -448
WIRE -88 -416 -88 -448
WIRE 24 -368 -88 -368
WIRE 88 -368 24 -368
WIRE 264 -352 264 -448
WIRE -184 -336 -264 -336
WIRE -136 -336 -184 -336
WIRE 88 -320 88 -368
WIRE -264 -304 -264 -336
WIRE -264 -176 -264 -224
WIRE -88 -176 -88 -320
WIRE 88 -176 88 -240
WIRE 264 -176 264 -272
WIRE 200 -96 -88 -96
WIRE 264 -96 200 -96
WIRE -88 -64 -88 -96
WIRE 24 -16 -88 -16
WIRE 88 -16 24 -16
WIRE 264 0 264 -96
WIRE -184 16 -264 16
WIRE -136 16 -184 16
WIRE 88 32 88 -16
WIRE -264 48 -264 16
WIRE -264 176 -264 128
WIRE -88 176 -88 32
WIRE 88 176 88 112
WIRE 264 176 264 80
WIRE -232 272 -264 272
WIRE -40 272 -88 272
WIRE -264 320 -264 272
WIRE -88 320 -88 272
WIRE -264 448 -264 400
WIRE -88 448 -88 400
FLAG -264 -176 0
FLAG 264 -176 0
FLAG -184 -336 g1
FLAG 88 -176 0
FLAG -88 -176 0
FLAG -264 176 0
FLAG 264 176 0
FLAG -184 16 g2
FLAG 200 -96 d2
FLAG 88 176 0
FLAG 24 -16 b2
FLAG -88 176 0
FLAG 24 -368 b1
FLAG 200 -448 d1
FLAG -264 448 0
FLAG -232 272 WL
FLAG -88 448 0
FLAG -40 272 GM
SYMBOL voltage 264 -368 R0
SYMATTR InstName VD1
SYMATTR Value {VDS}
SYMBOL voltage -264 -320 R0
SYMATTR Value2 AC 1
SYMATTR InstName VG1
SYMATTR Value {VGS}
SYMBOL nmos4 -136 -416 R0
SYMATTR Value2 l={L} w={W}
SYMATTR InstName M1
SYMATTR Value CMOSN
SYMBOL voltage 88 -336 R0
SYMATTR InstName VB1
SYMATTR Value {VBS}
SYMBOL voltage 264 -16 R0
SYMATTR InstName VD2
SYMATTR Value {VDS}
SYMBOL voltage -264 32 R0
SYMATTR InstName VG2
SYMATTR Value {VGS+1m}
SYMBOL voltage 88 16 R0
SYMATTR InstName VB2
SYMATTR Value {VBS}
SYMBOL nmos4 -136 -64 R0
SYMATTR Value2 l={L} w={W}
SYMATTR InstName M2
SYMATTR Value CMOSN
SYMBOL voltage -264 304 R0
SYMATTR InstName V1
SYMATTR Value {W_L}
SYMBOL bv -88 304 R0
SYMATTR InstName B1
SYMATTR Value V=(I(VD1)-I(VD2))*1000