difpair ckt - simple differential pair
*.width in=72
.opt acct list node lvlcod=2
*.tf v(5) vin
*.dc vin -0.25 0.25 0.005
*.ac dec 10 1 10ghz
.tran 5ns 500ns
vin 1 0 sin(0 0.1 5meg) ac 1
vcc 8 0 12
vee 9 0 -12
q1 4 2 6 qnl
q2 5 3 6 qnl
rs1 1 2 1k
rs2 3 0 1k
rc1 4 8 10k
rc2 5 8 10k
q3 6 7 9 qnl
q4 7 7 9 qnl
rbias 7 8 20k
.model qnl npn(bf=80 rb=100 ccs=2pf tf=0.3ns tr=6ns cje=3pf cjc=2pf
+   va=50)
.print dc v(4) v(5)
.plot dc v(5)
.print ac vm(5) vp(5)
.plot ac vm(5) vp(5)
.print tran v(4) v(5)
.plot tran v(5)
.end