* SPICE netlist
M1 N003 a vdd vdd PMOS
M2 N005 a vdd vdd PMOS
M3 N005 b vdd vdd PMOS
M4 N004 a vdd vdd PMOS
M5 N004 b vdd vdd PMOS
M6 N004 c vdd vdd PMOS
M7 m b N003 N003 PMOS
M8 m c N005 N005 PMOS
M9 N001 m N004 N004 PMOS
M10 N001 c N006 N006 PMOS
M11 N006 b N002 N002 PMOS
M12 N002 a vdd vdd PMOS
M13 sum N001 vdd vdd PMOS
M15 carru m vdd vdd PMOS
M14 m c N008 N008 NMOS
M16 m b N007 N007 NMOS
M17 N007 a 0 0 NMOS
M18 N008 a 0 0 NMOS
M19 N008 b 0 0 NMOS
M20 N001 m N010 N010 NMOS
M21 N010 a 0 0 NMOS
M22 N010 b 0 0 NMOS
M23 N010 c 0 0 NMOS
M24 N001 c N009 N009 NMOS
M25 N009 b N011 N011 NMOS
M26 N011 a 0 0 NMOS
M27 sum N001 0 0 NMOS
M28 carru m 0 0 NMOS
V1 a 0 PULSE(0 1.8 1p 1p 1p 10m 20m)
V2 b 0 PULSE(0 1.8 1p 1p 1p 20m 40m)
V3 c 0 PULSE(0 1.8 1p 1p 1p 40m 80m)
V4 vdd 0 1.8
.tran 100m

* LTspice schematic (.asc)
Version 4
SHEET 1 2432 992
WIRE -240 -368 -496 -368
WIRE -48 -368 -240 -368
WIRE 128 -368 -48 -368
WIRE 240 -368 128 -368
WIRE 400 -368 240 -368
WIRE 592 -368 400 -368
WIRE 1168 -368 1120 -368
WIRE -496 -336 -496 -368
WIRE -240 -336 -240 -368
WIRE -48 -336 -48 -368
WIRE 240 -336 240 -368
WIRE 400 -336 400 -368
WIRE 592 -336 592 -368
WIRE -48 -320 -48 -336
WIRE 992 -304 992 -368
WIRE 1216 -256 1216 -288
WIRE -480 -240 -496 -240
WIRE 400 -240 240 -240
WIRE 592 -240 400 -240
WIRE 1216 -224 1216 -256
WIRE -240 -192 -240 -240
WIRE -144 -192 -240 -192
WIRE -48 -192 -48 -240
WIRE -48 -192 -144 -192
WIRE 400 -192 400 -240
WIRE 416 -192 400 -192
WIRE -144 -160 -144 -192
WIRE 416 -160 416 -192
WIRE 992 -160 992 -208
WIRE 368 -144 304 -144
WIRE 1120 -144 1120 -368
WIRE 1168 -144 1120 -144
WIRE -480 -128 -480 -240
WIRE -480 16 -480 -32
WIRE -480 16 -512 16
WIRE -144 16 -144 -64
WIRE -144 16 -480 16
WIRE 304 16 304 -144
WIRE 304 16 -144 16
WIRE 416 16 416 -64
WIRE 992 16 992 -64
WIRE 992 16 416 16
WIRE 1120 16 1120 -144
WIRE 1120 16 992 16
WIRE 416 48 416 16
WIRE 432 48 416 48
WIRE 304 64 304 16
WIRE 992 80 992 16
WIRE 432 96 432 48
WIRE -512 112 -512 16
WIRE -144 112 -144 16
WIRE 1152 112 1136 112
WIRE 304 176 304 64
WIRE 384 176 304 176
WIRE -512 208 -512 192
WIRE -144 208 -144 192
WIRE 1120 224 1120 48
WIRE 1136 224 1136 112
WIRE 1136 224 1120 224
WIRE 1200 224 1200 192
WIRE 992 240 992 176
WIRE 432 256 432 192
WIRE 432 256 336 256
WIRE 480 256 432 256
WIRE 624 256 480 256
WIRE -144 272 -144 208
WIRE -144 272 -192 272
WIRE 16 272 -144 272
WIRE 336 272 336 256
WIRE 480 272 480 256
WIRE 624 272 624 256
WIRE 1200 272 1200 224
WIRE 1216 272 1200 272
WIRE 16 288 16 272
WIRE 1216 288 1216 272
WIRE -192 304 -192 272
WIRE 1216 304 1216 288
WIRE -512 320 -512 208
WIRE 480 368 336 368
WIRE 624 368 480 368
WIRE 1136 368 1136 224
WIRE 1168 368 1136 368
WIRE 1184 368 1168 368
WIRE 992 400 992 336
WIRE -192 416 -192 400
WIRE -192 416 -512 416
WIRE -80 416 -192 416
WIRE 16 416 16 384
WIRE 16 416 -80 416
WIRE 480 416 480 368
WIRE 480 416 16 416
WIRE 992 416 992 400
FLAG 992 496 0
FLAG 1216 -128 0
FLAG 1216 384 0
FLAG -80 416 0
FLAG -1216 -64 0
FLAG -1088 -224 0
FLAG -976 -400 0
FLAG -976 144 0
FLAG -1216 -144 a
FLAG -1088 -304 b
FLAG -976 -480 c
FLAG -976 64 vdd
FLAG 128 -368 vdd
FLAG 992 -464 vdd
FLAG 1216 -384 vdd
FLAG 1200 96 vdd
FLAG -544 -320 a
FLAG -288 -320 a
FLAG 192 -320 a
FLAG 944 -448 a
FLAG 944 480 a
FLAG 288 352 a
FLAG -240 384 a
FLAG -560 400 a
FLAG -528 -112 b
FLAG -560 192 b
FLAG -96 -320 b
FLAG -32 368 b
FLAG 432 352 b
FLAG 352 -320 b
FLAG -192 -144 c
FLAG -192 192 c
FLAG 576 352 c
FLAG 544 -320 c
FLAG 944 160 c
FLAG 944 -144 c
FLAG 944 -288 b
FLAG 944 320 b
FLAG 1216 -256 sum
FLAG 1200 224 carru
FLAG 304 64 m
FLAG 1120 48 m
SYMBOL pmos -544 -240 M180
SYMATTR InstName M1
SYMBOL pmos -288 -240 M180
SYMATTR InstName M2
SYMBOL pmos -96 -240 M180
SYMATTR InstName M3
SYMBOL pmos 192 -240 M180
SYMATTR InstName M4
SYMBOL pmos 352 -240 M180
SYMATTR InstName M5
SYMBOL pmos 544 -240 M180
SYMATTR InstName M6
SYMBOL pmos -528 -32 M180
SYMATTR InstName M7
SYMBOL pmos -192 -64 M180
SYMATTR InstName M8
SYMBOL pmos 368 -64 M180
SYMATTR InstName M9
SYMBOL pmos 944 -64 M180
SYMATTR InstName M10
SYMBOL pmos 944 -208 M180
SYMATTR InstName M11
SYMBOL pmos 944 -368 M180
SYMATTR InstName M12
SYMBOL pmos 1168 -288 M180
SYMATTR InstName M13
SYMBOL pmos 1152 192 M180
SYMATTR InstName M15
SYMBOL nmos -192 112 R0
SYMATTR InstName M14
SYMBOL nmos -560 112 R0
SYMATTR InstName M16
SYMBOL nmos -560 320 R0
SYMATTR InstName M17
SYMBOL nmos -240 304 R0
SYMATTR InstName M18
SYMBOL nmos -32 288 R0
SYMATTR InstName M19
SYMBOL nmos 384 96 R0
SYMATTR InstName M20
SYMBOL nmos 288 272 R0
SYMATTR InstName M21
SYMBOL nmos 432 272 R0
SYMATTR InstName M22
SYMBOL nmos 576 272 R0
SYMATTR InstName M23
SYMBOL nmos 944 80 R0
SYMATTR InstName M24
SYMBOL nmos 944 240 R0
SYMATTR InstName M25
SYMBOL nmos 944 400 R0
SYMATTR InstName M26
SYMBOL nmos 1168 -224 R0
SYMATTR InstName M27
SYMBOL nmos 1168 288 R0
SYMATTR InstName M28
SYMBOL voltage -1216 -160 R0
SYMATTR InstName V1
SYMATTR Value PULSE(0 1.8 1p 1p 1p 10m 20m)
SYMBOL voltage -1088 -320 R0
SYMATTR InstName V2
SYMATTR Value PULSE(0 1.8 1p 1p 1p 20m 40m)
SYMBOL voltage -976 -496 R0
SYMATTR InstName V3
SYMATTR Value PULSE(0 1.8 1p 1p 1p 40m 80m)
SYMBOL voltage -976 48 R0
SYMATTR InstName V4
SYMATTR Value 1.8