* simple differential pair with simple common-mode feedback

.model n1 nmos level=49 version=3.3.0 tox=3.5n nch=2.4e17 nsub=5e16 vth0=0.6
.model p1 pmos level=49 version=3.3.0 tox=3.5n nch=2.5e17 nsub=5e16 vth0=-0.7

.subckt diffpair inp inn outp outn setcm vdd vss
Mp1 outp cmfb vdd vdd p1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=4
Mp2 outn cmfb vdd vdd p1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=4
Mpcm cmfb cmfb vdd vdd p1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=2

Mncm cmfb setcm tail vss n1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=4
Mn1 outn inp tail vss n1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=8
Mn2 outp inn tail vss n1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=8

*bias
Mn0 tail bn vss vss n1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=4
Mnn bn bn vss vss n1 W=7.5u L=0.35u pd=13.5u ad=22.5p ps=13.5u as=22.5p m=4
Ib vss bn 1u
.ends

Xdiff inp inn outp outn setcm vdd vss diffpair
Cload outp outn 100f

:balun:Balun1 outp outn outcm outdiff
:balun:Balun1 inn inp incm indiff
Vprobediff outdiff indiff DC 0
Vprobecm outcm incm DC 0

Vset setcm vss DC 1.1
Vvdd vdd vss DC 3.3
Vvss vss 0 DC 0

.control
loop vprobediff dec 10 1 10e9 name="diffloop"
loop vprobecm dec 10 1 10e9 name="cmloop"
.endc