* SPICE netlist
C1 N006 0 10n
R1 N006 N001 910
R2 N001 N005 560
C2 N002 N001 10n
C3 N007 0 10n
R3 N007 N003 220
R4 N003 N002 390
C4 N004 N003 68n
V2 N005 0 AC 1
V1 +3V 0 3
C6 N017 0 10n
R7 N017 N008 910
R8 N008 N016 560
C7 N009 N008 10n
C8 N020 0 10n
R9 N020 N012 220
R10 N012 N009 390
C9 N013 N012 74n
V3 N016 0 AC 1
V4 +6V 0 6
XU6 N006 N002 +6V 0 N002 level4 Avol=600000 GBW=1Meg Slew=600000 Ilimit=25m Rail=0 Vos=0 Phimargin=45 En=0 Enk=0 In=0 Ink=0 Rin=500Meg Ro=1k Ccm=1p Cdiff=2p ;pnba In+)In-)V+)V-)OUT
XU1 N007 N004 +6V 0 N004 level4 Avol=600000 GBW=1Meg Slew=600000 Ilimit=25m Rail=0 Vos=0 Phimargin=45 En=0 Enk=0 In=0 Ink=0 Rin=500Meg Ro=1k Ccm=1p Cdiff=2p ;pnba In+)In-)V+)V-)OUT
XU5 N019 N011 NC_01 NC_02 N011 level1 Avol=1Meg GBW=10Meg Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
XU7 N021 N015 NC_03 NC_04 N015 level1 Avol=1Meg GBW=10Meg Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
C14 N019 0 10n
R15 N019 N010 910
R16 N010 N018 560
C15 N011 N010 10n
C16 N021 0 10n
R17 N021 N014 220
R18 N014 N011 390
C17 N015 N014 74n
V6 N018 0 AC 1
XU2 N017 N009 +6V 0 N009 level4 Avol=600000 GBW=1Meg Slew=600000 Ilimit=25m Rail=0 Vos=0 Phimargin=45 En=0 Enk=0 In=0 Ink=0 Rin=500Meg Ro=1k Ccm=1p Cdiff=2p ;pnba In+)In-)V+)V-)OUT
XU4 N020 N013 +6V 0 N013 level4 Avol=600000 GBW=1Meg Slew=600000 Ilimit=25m Rail=0 Vos=0 Phimargin=45 En=0 Enk=0 In=0 Ink=0 Rin=500Meg Ro=1k Ccm=1p Cdiff=2p ;pnba In+)In-)V+)V-)OUT
.ac dec 1000 10 1e+6

* LTspice schematic (.asc)
Version 4
SHEET 1 2416 784
WIRE -792 -376 -1000 -376
WIRE -648 -376 -728 -376
WIRE -280 -360 -488 -360
WIRE -136 -360 -216 -360
WIRE 440 -296 440 -328
WIRE -712 -280 -712 -328
WIRE 184 -280 184 -312
WIRE -1112 -264 -1208 -264
WIRE -1000 -264 -1000 -376
WIRE -1000 -264 -1032 -264
WIRE -968 -264 -1000 -264
WIRE -856 -264 -888 -264
WIRE -744 -264 -856 -264
WIRE -200 -264 -200 -296
WIRE -648 -248 -648 -376
WIRE -648 -248 -680 -248
WIRE -600 -248 -648 -248
WIRE -488 -248 -488 -360
WIRE -488 -248 -520 -248
WIRE -456 -248 -488 -248
WIRE -344 -248 -376 -248
WIRE -232 -248 -344 -248
WIRE -1208 -232 -1208 -264
WIRE -856 -232 -856 -264
WIRE -744 -232 -776 -232
WIRE -136 -232 -136 -360
WIRE -136 -232 -168 -232
WIRE -344 -216 -344 -248
WIRE -232 -216 -264 -216
WIRE 440 -184 440 -216
WIRE -776 -168 -776 -232
WIRE -648 -168 -648 -248
WIRE -648 -168 -776 -168
WIRE 184 -168 184 -200
WIRE -264 -152 -264 -216
WIRE -136 -152 -136 -232
WIRE -136 -152 -264 -152
WIRE -856 -136 -856 -168
WIRE -344 -120 -344 -152
WIRE -1208 -104 -1208 -152
WIRE -792 120 -1000 120
WIRE -648 120 -728 120
WIRE 552 120 344 120
WIRE 696 120 616 120
WIRE -280 136 -488 136
WIRE -136 136 -216 136
WIRE 1064 136 856 136
WIRE 1208 136 1128 136
WIRE -712 216 -712 184
WIRE -1112 232 -1208 232
WIRE -1000 232 -1000 120
WIRE -1000 232 -1032 232
WIRE -968 232 -1000 232
WIRE -856 232 -888 232
WIRE -744 232 -856 232
WIRE -200 232 -200 200
WIRE 232 232 136 232
WIRE 344 232 344 120
WIRE 344 232 312 232
WIRE 376 232 344 232
WIRE 488 232 456 232
WIRE 600 232 488 232
WIRE -648 248 -648 120
WIRE -648 248 -680 248
WIRE -600 248 -648 248
WIRE -488 248 -488 136
WIRE -488 248 -520 248
WIRE -456 248 -488 248
WIRE -344 248 -376 248
WIRE -232 248 -344 248
WIRE 696 248 696 120
WIRE 696 248 664 248
WIRE 744 248 696 248
WIRE 856 248 856 136
WIRE 856 248 824 248
WIRE 888 248 856 248
WIRE 1000 248 968 248
WIRE 1112 248 1000 248
WIRE -1208 264 -1208 232
WIRE -856 264 -856 232
WIRE -744 264 -776 264
WIRE -136 264 -136 136
WIRE -136 264 -168 264
WIRE 136 264 136 232
WIRE 488 264 488 232
WIRE 600 264 568 264
WIRE 1208 264 1208 136
WIRE 1208 264 1176 264
WIRE -344 280 -344 248
WIRE -232 280 -264 280
WIRE 1000 280 1000 248
WIRE 1112 280 1080 280
WIRE -776 328 -776 264
WIRE -648 328 -648 248
WIRE -648 328 -776 328
WIRE 568 328 568 264
WIRE 696 328 696 248
WIRE 696 328 568 328
WIRE -264 344 -264 280
WIRE -136 344 -136 264
WIRE -136 344 -264 344
WIRE 1080 344 1080 280
WIRE 1208 344 1208 264
WIRE 1208 344 1080 344
WIRE -856 360 -856 328
WIRE 488 360 488 328
WIRE -344 376 -344 344
WIRE 1000 376 1000 344
WIRE -1208 392 -1208 344
WIRE 136 392 136 344
FLAG -856 -136 0
FLAG -344 -120 0
FLAG -1208 -104 0
FLAG 184 -168 0
FLAG 184 -312 +3V
FLAG -856 360 0
FLAG -344 376 0
FLAG -1208 392 0
FLAG 440 -184 0
FLAG 440 -328 +6V
FLAG -200 -296 0
FLAG -712 -216 +6V
FLAG -200 -200 +6V
FLAG -712 -328 0
FLAG -200 200 0
FLAG -200 296 +6V
FLAG -712 184 0
FLAG -712 280 +6V
FLAG 488 360 0
FLAG 1000 376 0
FLAG 136 392 0
SYMBOL cap -872 -232 R0
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL res -872 -280 R90
SYMATTR InstName R1
SYMATTR Value 910
SYMBOL res -1016 -280 R90
SYMATTR InstName R2
SYMATTR Value 560
SYMBOL cap -728 -392 R90
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL cap -360 -216 R0
SYMATTR InstName C3
SYMATTR Value 10n
SYMBOL res -360 -264 R90
SYMATTR InstName R3
SYMATTR Value 220
SYMBOL res -504 -264 R90
SYMATTR InstName R4
SYMATTR Value 390
SYMBOL cap -216 -376 R90
SYMATTR InstName C4
SYMATTR Value 68n
SYMBOL voltage -1208 -248 R0
SYMATTR Value ""
SYMATTR Value2 AC 1
SYMATTR InstName V2
SYMBOL voltage 184 -296 R0
SYMATTR InstName V1
SYMATTR Value 3
SYMBOL cap -872 264 R0
SYMATTR InstName C6
SYMATTR Value 10n
SYMBOL res -872 216 R90
SYMATTR InstName R7
SYMATTR Value 910
SYMBOL res -1016 216 R90
SYMATTR InstName R8
SYMATTR Value 560
SYMBOL cap -728 104 R90
SYMATTR InstName C7
SYMATTR Value 10n
SYMBOL cap -360 280 R0
SYMATTR InstName C8
SYMATTR Value 10n
SYMBOL res -360 232 R90
SYMATTR InstName R9
SYMATTR Value 220
SYMBOL res -504 232 R90
SYMATTR InstName R10
SYMATTR Value 390
SYMBOL cap -216 120 R90
SYMATTR InstName C9
SYMATTR Value 74n
SYMBOL voltage -1208 248 R0
SYMATTR Value ""
SYMATTR Value2 AC 1
SYMATTR InstName V3
SYMBOL voltage 440 -312 R0
SYMATTR InstName V4
SYMATTR Value 6
SYMBOL OpAmps\\UniversalOpAmp4 -712 -248 M180
SYMATTR InstName U6
SYMATTR Value2 Avol=600000 GBW=1Meg Slew=600000
SYMBOL OpAmps\\UniversalOpAmp4 -200 -232 M180
SYMATTR InstName U1
SYMATTR Value2 Avol=600000 GBW=1Meg Slew=600000
SYMBOL OpAmps\\UniversalOpAmp 632 248 M180
SYMATTR InstName U5
SYMBOL OpAmps\\UniversalOpAmp 1144 264 M180
SYMATTR InstName U7
SYMBOL cap 472 264 R0
SYMATTR InstName C14
SYMATTR Value 10n
SYMBOL res 472 216 R90
SYMATTR InstName R15
SYMATTR Value 910
SYMBOL res 328 216 R90
SYMATTR InstName R16
SYMATTR Value 560
SYMBOL cap 616 104 R90
SYMATTR InstName C15
SYMATTR Value 10n
SYMBOL cap 984 280 R0
SYMATTR InstName C16
SYMATTR Value 10n
SYMBOL res 984 232 R90
SYMATTR InstName R17
SYMATTR Value 220
SYMBOL res 840 232 R90
SYMATTR InstName R18
SYMATTR Value 390
SYMBOL cap 1128 120 R90
SYMATTR InstName C17
SYMATTR Value 74n
SYMBOL voltage 136 248 R0
SYMATTR Value ""
SYMATTR Value2 AC 1
SYMATTR InstName V6
SYMBOL OpAmps\\UniversalOpAmp4 -712 248 M180
SYMATTR InstName U2
SYMATTR Value2 Avol=600000 GBW=1Meg Slew=600000
SYMBOL OpAmps\\UniversalOpAmp4 -200 264 M180
SYMATTR InstName U4
SYMATTR Value2 Avol=600000 GBW=1Meg Slew=600000