* SPICE netlist
M1 N001 Osc 0 0 N_50n l=50n w=500n
VDD VDD 0 1
M2 VDD Osc N001 VDD P_50n l=50n w=1u
M3 N002 N001 0 0 N_50n l=50n w=500n
M4 VDD N001 N002 VDD P_50n l=50n w=1u
M5 N003 N002 0 0 N_50n l=50n w=500n
M6 VDD N002 N003 VDD P_50n l=50n w=1u
M7 N004 N003 0 0 N_50n l=50n w=500n
M8 VDD N003 N004 VDD P_50n l=50n w=1u
M9 N005 N004 0 0 N_50n l=50n w=500n
M10 VDD N004 N005 VDD P_50n l=50n w=1u
M11 N006 N005 0 0 N_50n l=50n w=500n
M12 VDD N005 N006 VDD P_50n l=50n w=1u
M13 N007 N006 0 0 N_50n l=50n w=500n
M14 VDD N006 N007 VDD P_50n l=50n w=1u
M15 N008 N007 0 0 N_50n l=50n w=500n
M16 VDD N007 N008 VDD P_50n l=50n w=1u
M17 N009 N008 0 0 N_50n l=50n w=500n
M18 VDD N008 N009 VDD P_50n l=50n w=1u
M19 N010 N009 0 0 N_50n l=50n w=500n
M20 VDD N009 N010 VDD P_50n l=50n w=1u
M21 Osc N010 0 0 N_50n l=50n w=500n
M22 VDD N010 Osc VDD P_50n l=50n w=1u
.tran 0 2n 0 1p
.ic v(osc)=1

* LTspice schematic (.asc)
Version 4
SHEET 1 2848 592
WIRE -1424 -40 -1424 -296
WIRE -1376 -40 -1424 -40
WIRE -1376 -40 -1376 -88
WIRE -1376 40 -1376 -40
WIRE -1344 -88 -1376 -88
WIRE -1344 40 -1376 40
WIRE -1296 -168 -1296 -216
WIRE -1296 -40 -1296 -72
WIRE -1296 104 -1296 56
WIRE -1120 -40 -1296 -40
WIRE -1120 -40 -1120 -88
WIRE -1120 40 -1120 -40
WIRE -1088 -88 -1120 -88
WIRE -1088 40 -1120 40
WIRE -1040 -168 -1040 -216
WIRE -1040 -40 -1040 -72
WIRE -1040 104 -1040 56
WIRE -864 -40 -1040 -40
WIRE -864 -40 -864 -88
WIRE -864 40 -864 -40
WIRE -832 -88 -864 -88
WIRE -832 40 -864 40
WIRE -784 -168 -784 -216
WIRE -784 -40 -784 -72
WIRE -784 104 -784 56
WIRE -768 168 -768 152
WIRE -768 184 -768 168
WIRE -768 296 -768 264
WIRE -608 -40 -784 -40
WIRE -608 -40 -608 -88
WIRE -608 40 -608 -40
WIRE -576 -88 -608 -88
WIRE -576 40 -608 40
WIRE -528 -168 -528 -216
WIRE -528 -40 -528 -72
WIRE -528 104 -528 56
WIRE -352 -40 -528 -40
WIRE -352 -40 -352 -88
WIRE -352 40 -352 -40
WIRE -320 -88 -352 -88
WIRE -320 40 -352 40
WIRE -272 -168 -272 -216
WIRE -272 -40 -272 -72
WIRE -272 104 -272 56
WIRE -96 -40 -272 -40
WIRE -96 -40 -96 -88
WIRE -96 40 -96 -40
WIRE -64 -88 -96 -88
WIRE -64 40 -96 40
WIRE -16 -168 -16 -216
WIRE -16 -40 -16 -72
WIRE -16 104 -16 56
WIRE 160 -40 -16 -40
WIRE 160 -40 160 -88
WIRE 160 40 160 -40
WIRE 192 -88 160 -88
WIRE 192 40 160 40
WIRE 240 -168 240 -216
WIRE 240 -40 240 -72
WIRE 240 104 240 56
WIRE 368 -296 -1424 -296
WIRE 416 -40 240 -40
WIRE 416 -40 416 -88
WIRE 416 40 416 -40
WIRE 448 -88 416 -88
WIRE 448 40 416 40
WIRE 496 -168 496 -216
WIRE 496 -40 496 -72
WIRE 496 104 496 56
WIRE 656 -40 496 -40
WIRE 656 -40 656 -88
WIRE 656 40 656 -40
WIRE 688 -88 656 -88
WIRE 688 40 656 40
WIRE 736 -168 736 -216
WIRE 736 -40 736 -72
WIRE 736 104 736 56
WIRE 912 -40 736 -40
WIRE 912 -40 912 -88
WIRE 912 40 912 -40
WIRE 944 -88 912 -88
WIRE 944 40 912 40
WIRE 992 -168 992 -216
WIRE 992 -40 992 -72
WIRE 992 104 992 56
WIRE 1168 -40 992 -40
WIRE 1168 -40 1168 -88
WIRE 1168 40 1168 -40
WIRE 1200 -88 1168 -88
WIRE 1200 40 1168 40
WIRE 1248 -168 1248 -216
WIRE 1248 -40 1248 -72
WIRE 1248 104 1248 56
WIRE 1424 -296 368 -296
WIRE 1424 -40 1248 -40
WIRE 1424 -40 1424 -296
FLAG -1296 8 0
FLAG -768 296 0
FLAG -768 168 VDD
FLAG -1296 -120 VDD
FLAG -1296 104 0
FLAG -1296 -216 VDD
FLAG -1040 8 0
FLAG -1040 -120 VDD
FLAG -1040 104 0
FLAG -1040 -216 VDD
FLAG -784 8 0
FLAG -784 -120 VDD
FLAG -784 104 0
FLAG -784 -216 VDD
FLAG -528 8 0
FLAG -528 -120 VDD
FLAG -528 104 0
FLAG -528 -216 VDD
FLAG -272 8 0
FLAG -272 -120 VDD
FLAG -272 104 0
FLAG -272 -216 VDD
FLAG -16 8 0
FLAG -16 -120 VDD
FLAG -16 104 0
FLAG -16 -216 VDD
FLAG 240 8 0
FLAG 240 -120 VDD
FLAG 240 104 0
FLAG 240 -216 VDD
FLAG 496 8 0
FLAG 496 -120 VDD
FLAG 496 104 0
FLAG 496 -216 VDD
FLAG 736 8 0
FLAG 736 -120 VDD
FLAG 736 104 0
FLAG 736 -216 VDD
FLAG 992 8 0
FLAG 992 -120 VDD
FLAG 992 104 0
FLAG 992 -216 VDD
FLAG 1248 8 0
FLAG 1248 -120 VDD
FLAG 1248 104 0
FLAG 1248 -216 VDD
FLAG 368 -296 Osc
SYMBOL nmos4 -1344 -40 R0
SYMATTR InstName M1
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL voltage -768 168 R0
SYMATTR InstName VDD
SYMATTR Value 1
SYMBOL pmos4 -1344 -168 R0
SYMATTR InstName M2
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 -1088 -40 R0
SYMATTR InstName M3
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 -1088 -168 R0
SYMATTR InstName M4
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 -832 -40 R0
SYMATTR InstName M5
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 -832 -168 R0
SYMATTR InstName M6
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 -576 -40 R0
SYMATTR InstName M7
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 -576 -168 R0
SYMATTR InstName M8
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 -320 -40 R0
SYMATTR InstName M9
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 -320 -168 R0
SYMATTR InstName M10
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 -64 -40 R0
SYMATTR InstName M11
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 -64 -168 R0
SYMATTR InstName M12
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 192 -40 R0
SYMATTR InstName M13
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 192 -168 R0
SYMATTR InstName M14
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 448 -40 R0
SYMATTR InstName M15
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 448 -168 R0
SYMATTR InstName M16
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 688 -40 R0
SYMATTR InstName M17
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 688 -168 R0
SYMATTR InstName M18
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 944 -40 R0
SYMATTR InstName M19
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 944 -168 R0
SYMATTR InstName M20
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u
SYMBOL nmos4 1200 -40 R0
SYMATTR InstName M21
SYMATTR Value N_50n
SYMATTR Value2 l=50n w=500n
SYMBOL pmos4 1200 -168 R0
SYMATTR InstName M22
SYMATTR Value P_50n
SYMATTR Value2 l=50n w=1u