* SPICE netlist
M1 N002 N005 N006 N003 PMOS
M2 N002 N001 N007 N004 PMOS
M3 N006 N010 SUM N008 PMOS
M4 N007 N012 SUM N009 PMOS
M5 N011 N005 N010 N011 PMOS
M6 N010 N005 0 0 NMOS
V1 N011 0 5
V2 N002 0 5
M7 N013 N001 N012 N013 PMOS
M8 N012 N001 0 0 NMOS
V5 N013 0 5
M9 SUM N005 N016 N014 NMOS
M10 N016 N001 0 N018 NMOS
M11 SUM N010 N017 N015 NMOS
M12 N017 N012 0 N019 NMOS
M13 N020 N005 N022 N020 PMOS l=1040nm w=1040nm
M14 N022 N005 N024 0 NMOS l=1040nm w=1040nm
M15 N024 N001 0 0 NMOS l=1040nm w=1040nm
V6 N020 0 3.3
M16 N020 N001 N022 N020 PMOS
M17 N020 N022 Carry N021 PMOS
M18 Carry N022 0 N023 NMOS
VA N005 0 PULSE(0 5 0 5n 5n 20m 40m)
Vb N001 0 PULSE(0 5 0 5n 5n 10m 20m)
.tran 80m

* LTspice schematic (.asc)
Version 4
SHEET 1 1904 2080
WIRE 776 -1040 -840 -1040
WIRE 248 -912 136 -912
WIRE 392 -912 248 -912
WIRE 136 -864 136 -896
WIRE 392 -864 392 -896
WIRE 344 -752 344 -832
WIRE 440 -752 344 -752
WIRE -488 -704 -952 -704
WIRE -360 -704 -488 -704
WIRE -8 -704 -360 -704
WIRE 88 -704 88 -832
WIRE 88 -704 -8 -704
WIRE 440 -704 440 -752
WIRE 744 -704 440 -704
WIRE 776 -704 776 -1040
WIRE 776 -704 744 -704
WIRE 136 -688 136 -816
WIRE 392 -688 392 -816
WIRE -840 -656 -840 -1040
WIRE -568 -656 -840 -656
WIRE 136 -640 136 -672
WIRE 392 -640 392 -672
WIRE 600 -624 584 -624
WIRE -952 -608 -952 -704
WIRE -840 -608 -840 -656
WIRE 88 -608 88 -624
WIRE -200 -592 -216 -592
WIRE 248 -592 136 -592
WIRE 392 -592 248 -592
WIRE -952 -576 -952 -608
WIRE 584 -576 584 -624
WIRE 600 -576 584 -576
WIRE -200 -544 -200 -592
WIRE -200 -544 -216 -544
WIRE 344 -496 344 -608
WIRE 552 -496 344 -496
WIRE 600 -496 600 -528
WIRE 600 -496 552 -496
WIRE 648 -496 648 -608
WIRE 744 -496 744 -704
WIRE 744 -496 648 -496
WIRE -360 -464 -360 -704
WIRE -264 -464 -264 -512
WIRE -264 -464 -360 -464
WIRE -216 -464 -216 -496
WIRE 88 -464 88 -608
WIRE 88 -464 -216 -464
WIRE 392 -464 88 -464
WIRE 600 -464 600 -496
WIRE 648 -448 648 -496
WIRE -216 -432 -216 -464
WIRE 600 -416 584 -416
WIRE -200 -384 -216 -384
WIRE 584 -368 584 -416
WIRE 600 -368 584 -368
WIRE -264 -352 -264 -464
WIRE -200 -336 -200 -384
WIRE -200 -336 -216 -336
WIRE 248 -192 248 -592
WIRE 952 -192 248 -192
WIRE 248 -112 248 -192
WIRE 248 -112 120 -112
WIRE 440 -112 248 -112
WIRE -8 -32 -8 -704
WIRE 72 -32 -8 -32
WIRE 120 -32 120 -64
WIRE 392 -32 392 -464
WIRE 440 -32 440 -64
WIRE 120 64 120 -16
WIRE 440 64 440 -16
WIRE 120 144 120 112
WIRE 440 144 440 112
WIRE 264 160 120 160
WIRE 440 160 264 160
WIRE 72 208 72 144
WIRE 776 208 776 -704
WIRE 776 208 72 208
WIRE 392 256 392 144
WIRE 552 256 552 -496
WIRE 552 256 392 256
WIRE 232 416 232 384
WIRE 232 496 152 496
WIRE 152 512 152 496
WIRE 152 512 136 512
WIRE 136 528 136 512
WIRE 232 528 232 496
WIRE 312 528 232 528
WIRE 328 528 312 528
WIRE 488 528 328 528
WIRE 152 576 152 512
WIRE 152 576 136 576
WIRE 328 576 328 528
WIRE 328 576 312 576
WIRE 488 576 488 544
WIRE 88 608 56 608
WIRE 600 624 488 624
WIRE 264 640 264 608
WIRE 264 640 72 640
WIRE 136 656 136 624
WIRE 312 656 312 624
WIRE 312 656 136 656
WIRE 440 656 440 608
WIRE 440 656 312 656
WIRE -488 704 -488 -704
WIRE 56 704 56 608
WIRE 56 704 -488 704
WIRE 440 704 440 656
WIRE 488 704 488 672
WIRE 136 720 136 656
WIRE 168 768 136 768
WIRE 56 800 56 704
WIRE 88 800 56 800
WIRE 136 816 136 800
WIRE 136 896 136 816
WIRE 168 944 168 768
WIRE 168 944 136 944
WIRE -568 976 -568 -656
WIRE 72 976 72 640
WIRE 72 976 -568 976
WIRE 88 976 72 976
WIRE 168 992 168 944
WIRE 168 992 136 992
WIRE 488 992 488 720
WIRE 488 992 168 992
WIRE 136 1040 136 992
FLAG -200 -336 0
FLAG -216 -672 0
FLAG 248 -992 0
FLAG 584 -624 0
FLAG 600 -288 0
FLAG 952 -192 SUM
IOPIN 1296 128 Out
FLAG 264 160 0
FLAG 136 1040 0
FLAG 232 384 0
FLAG 600 624 Carry
IOPIN 944 944 Out
FLAG -840 -528 0
FLAG -952 -528 0
SYMBOL pmos4 88 -912 R0
SYMATTR InstName M1
SYMBOL pmos4 344 -912 R0
SYMATTR InstName M2
SYMBOL pmos4 88 -688 R0
SYMATTR InstName M3
SYMBOL pmos4 344 -688 R0
SYMATTR InstName M4
SYMBOL pmos4 -264 -592 R0
SYMATTR InstName M5
SYMBOL nmos4 -264 -432 R0
SYMATTR InstName M6
SYMBOL voltage -216 -576 R180
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL voltage 248 -896 R180
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL pmos4 648 -368 R180
SYMATTR InstName M7
SYMBOL nmos4 648 -528 R180
SYMATTR InstName M8
SYMBOL voltage 600 -384 R0
SYMATTR InstName V5
SYMATTR Value 5
SYMBOL nmos4 72 -112 R0
SYMATTR InstName M9
SYMBOL nmos4 72 64 R0
SYMATTR InstName M10
SYMBOL nmos4 392 -112 R0
SYMATTR InstName M11
SYMBOL nmos4 392 64 R0
SYMATTR InstName M12
SYMBOL pmos4 88 528 R0
SYMATTR InstName M13
SYMATTR Value2 l=1040nm w=1040nm
SYMBOL nmos4 88 720 R0
SYMATTR InstName M14
SYMATTR Value2 l=1040nm w=1040nm
SYMBOL nmos4 88 896 R0
SYMATTR InstName M15
SYMATTR Value2 l=1040nm w=1040nm
SYMBOL voltage 232 512 R180
SYMATTR InstName V6
SYMATTR Value 3.3
SYMBOL pmos4 264 528 R0
SYMATTR InstName M16
SYMBOL pmos4 440 528 R0
SYMATTR InstName M17
SYMBOL nmos4 440 624 R0
SYMATTR InstName M18
SYMBOL voltage -952 -624 R0
SYMATTR InstName A
SYMATTR Value PULSE(0 5 0 5n 5n 20m 40m)
SYMBOL voltage -840 -624 R0
SYMATTR InstName b
SYMATTR Value PULSE(0 5 0 5n 5n 10m 20m)