* SPICE netlist
R1 N017 N016 500k
C1 N017 0 700n
R2 N018 N017 500k
C2 N018 0 700n
R3 N019 N018 500k
C3 N019 0 700n
V1 N016 0 PULSE(0 5 0 1n 1n 0.2 0.4)
R4 N020 N019 500k
C4 N020 0 700n
R5 N012 N011 500k
C5 N012 0 700n
R6 N013 N012 500k
C6 N013 0 700n
R7 N014 N013 500k
C7 N014 0 700n
V2 N011 0 PULSE(0 5 0 1n 1n 0.29 0.5)
R8 N015 N014 500k
C8 N015 0 700n
R9 N007 N006 500k
C9 N007 0 700n
R10 N008 N007 500k
C10 N008 0 700n
R11 N009 N008 500k
C11 N009 0 700n
V3 N006 0 PULSE(0 5 0 1n 1n 0.42 0.667)
R12 N010 N009 500k
C12 N010 0 700n
R13 N002 N001 500k
C13 N002 0 700n
R14 N003 N002 500k
C14 N003 0 700n
R15 N004 N003 500k
C15 N004 0 700n
V4 N001 0 PULSE(0 5 0 1n 1n 0.7 1)
R16 N005 N004 500k
C16 N005 0 700n

* LTspice schematic (.asc)
Version 4
SHEET 1 976 1440
WIRE -488 -512 -488 -640
WIRE -232 -512 -488 -512
WIRE -120 -512 -152 -512
WIRE -72 -512 -120 -512
WIRE 40 -512 8 -512
WIRE 88 -512 40 -512
WIRE 200 -512 168 -512
WIRE 264 -512 200 -512
WIRE 376 -512 344 -512
WIRE 440 -512 376 -512
WIRE -120 -496 -120 -512
WIRE 40 -496 40 -512
WIRE 200 -496 200 -512
WIRE 376 -496 376 -512
WIRE -120 -416 -120 -432
WIRE 40 -416 40 -432
WIRE 200 -416 200 -432
WIRE 376 -416 376 -432
WIRE -472 -176 -472 -304
WIRE -216 -176 -472 -176
WIRE -104 -176 -136 -176
WIRE -56 -176 -104 -176
WIRE 56 -176 24 -176
WIRE 104 -176 56 -176
WIRE 216 -176 184 -176
WIRE 280 -176 216 -176
WIRE 392 -176 360 -176
WIRE 456 -176 392 -176
WIRE -104 -160 -104 -176
WIRE 56 -160 56 -176
WIRE 216 -160 216 -176
WIRE 392 -160 392 -176
WIRE -104 -80 -104 -96
WIRE 56 -80 56 -96
WIRE 216 -80 216 -96
WIRE 392 -80 392 -96
WIRE -456 288 -456 160
WIRE -200 288 -456 288
WIRE -88 288 -120 288
WIRE -40 288 -88 288
WIRE 72 288 40 288
WIRE 120 288 72 288
WIRE 232 288 200 288
WIRE 296 288 232 288
WIRE 408 288 376 288
WIRE 472 288 408 288
WIRE -88 304 -88 288
WIRE 72 304 72 288
WIRE 232 304 232 288
WIRE 408 304 408 288
WIRE -88 384 -88 368
WIRE 72 384 72 368
WIRE 232 384 232 368
WIRE 408 384 408 368
WIRE -440 624 -440 496
WIRE -184 624 -440 624
WIRE -72 624 -104 624
WIRE -24 624 -72 624
WIRE 88 624 56 624
WIRE 136 624 88 624
WIRE 248 624 216 624
WIRE 312 624 248 624
WIRE 424 624 392 624
WIRE 488 624 424 624
WIRE -72 640 -72 624
WIRE 88 640 88 624
WIRE 248 640 248 624
WIRE 424 640 424 624
WIRE -72 720 -72 704
WIRE 88 720 88 704
WIRE 248 720 248 704
WIRE 424 720 424 704
FLAG -72 720 0
FLAG 88 720 0
FLAG 248 720 0
FLAG -440 416 0
FLAG 424 720 0
FLAG -88 384 0
FLAG 72 384 0
FLAG 232 384 0
FLAG -456 80 0
FLAG 408 384 0
FLAG -104 -80 0
FLAG 56 -80 0
FLAG 216 -80 0
FLAG -472 -384 0
FLAG 392 -80 0
FLAG -120 -416 0
FLAG 40 -416 0
FLAG 200 -416 0
FLAG -488 -720 0
FLAG 376 -416 0
SYMBOL res -88 608 R90
SYMATTR InstName R1
SYMATTR Value 500k
SYMBOL cap -88 640 R0
SYMATTR InstName C1
SYMATTR Value 700n
SYMBOL res 72 608 R90
SYMATTR InstName R2
SYMATTR Value 500k
SYMBOL cap 72 640 R0
SYMATTR InstName C2
SYMATTR Value 700n
SYMBOL res 232 608 R90
SYMATTR InstName R3
SYMATTR Value 500k
SYMBOL cap 232 640 R0
SYMATTR InstName C3
SYMATTR Value 700n
SYMBOL voltage -440 512 R180
SYMATTR InstName V1
SYMATTR Value PULSE(0 5 0 1n 1n 0.2 0.4)
SYMBOL res 408 608 R90
SYMATTR InstName R4
SYMATTR Value 500k
SYMBOL cap 408 640 R0
SYMATTR InstName C4
SYMATTR Value 700n
SYMBOL res -104 272 R90
SYMATTR InstName R5
SYMATTR Value 500k
SYMBOL cap -104 304 R0
SYMATTR InstName C5
SYMATTR Value 700n
SYMBOL res 56 272 R90
SYMATTR InstName R6
SYMATTR Value 500k
SYMBOL cap 56 304 R0
SYMATTR InstName C6
SYMATTR Value 700n
SYMBOL res 216 272 R90
SYMATTR InstName R7
SYMATTR Value 500k
SYMBOL cap 216 304 R0
SYMATTR InstName C7
SYMATTR Value 700n
SYMBOL voltage -456 176 R180
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 0 1n 1n 0.29 0.5)
SYMBOL res 392 272 R90
SYMATTR InstName R8
SYMATTR Value 500k
SYMBOL cap 392 304 R0
SYMATTR InstName C8
SYMATTR Value 700n
SYMBOL res -120 -192 R90
SYMATTR InstName R9
SYMATTR Value 500k
SYMBOL cap -120 -160 R0
SYMATTR InstName C9
SYMATTR Value 700n
SYMBOL res 40 -192 R90
SYMATTR InstName R10
SYMATTR Value 500k
SYMBOL cap 40 -160 R0
SYMATTR InstName C10
SYMATTR Value 700n
SYMBOL res 200 -192 R90
SYMATTR InstName R11
SYMATTR Value 500k
SYMBOL cap 200 -160 R0
SYMATTR InstName C11
SYMATTR Value 700n
SYMBOL voltage -472 -288 R180
SYMATTR InstName V3
SYMATTR Value PULSE(0 5 0 1n 1n 0.42 0.667)
SYMBOL res 376 -192 R90
SYMATTR InstName R12
SYMATTR Value 500k
SYMBOL cap 376 -160 R0
SYMATTR InstName C12
SYMATTR Value 700n
SYMBOL res -136 -528 R90
SYMATTR InstName R13
SYMATTR Value 500k
SYMBOL cap -136 -496 R0
SYMATTR InstName C13
SYMATTR Value 700n
SYMBOL res 24 -528 R90
SYMATTR InstName R14
SYMATTR Value 500k
SYMBOL cap 24 -496 R0
SYMATTR InstName C14
SYMATTR Value 700n
SYMBOL res 184 -528 R90
SYMATTR InstName R15
SYMATTR Value 500k
SYMBOL cap 184 -496 R0
SYMATTR InstName C15
SYMATTR Value 700n
SYMBOL voltage -488 -624 R180
SYMATTR InstName V4
SYMATTR Value PULSE(0 5 0 1n 1n 0.7 1)
SYMBOL res 360 -528 R90
SYMATTR InstName R16
SYMATTR Value 500k
SYMBOL cap 360 -496 R0
SYMATTR InstName C16
SYMATTR Value 700n