* SPICE netlist
V1 Vi_P 0 SINE(0 5m 10k) AC 1
V2 Vcc 0 5
V3 Vss 0 -5
V4 Vcm 0 2.048
R5 N003 N005 {R1} noiseless
R6 V_amp_P N003 {R2} noiseless
R12 V_amp_N N005 {R2} noiseless
V5 0 Vi_N SINE(0 5m 10k)
R7 N001 V_amp_P {R_flt} noiseless
R8 N006 V_amp_N {R_flt} noiseless
R9 V_fltr_P Vo_P {R_flt}
R10 V_fltr_N Vo_N {R_flt}
C1 N001 0 {C_flt} noiseless
C2 0 N006 {C_flt} noiseless
C3 V_fltr_P 0 {C_flt}
C4 0 V_fltr_N {C_flt}
XU1 Vi_P N003 V_amp_P Vcc Vss Vcc LTC6228 ;pnba IN+)IN-)OUT)VCC)VEE)SHDN_L
XU2 Vi_N N005 V_amp_N Vcc Vss Vcc LTC6228 ;pnba IN+)IN-)OUT)VCC)VEE)SHDN_L
R1 N002 N001 250
R2 N004 N006 250
R3 Vo_P N002 5000
R4 Vo_N N004 5000
XU4 N004 Vcm Vcc NC_01 NC_02 Vss Vcc N002 Vo_P Vo_N LTC6404-1 ;pnba IN-)Vocm)V+)OUT+)OUT-)V-)_SHDN)IN+)OUTF-)OUTF+
;.ac dec 100000 1 2G
.tran 0 100u 10u
;.noise V(V_amp_P,V_amp_N) V1 dec 100000 10k 7.5Meg
;.noise V(V_fltr_P,V_fltr_N) V1 dec 100000 10k 7.5Meg
.param R1=25
.param R2={R1*20}
.param R_flt=250
.param C_flt=85p

* LTspice schematic (.asc)
Version 4
SHEET 1 3968 768
WIRE -992 -368 -992 -384
WIRE -944 -368 -944 -384
WIRE -1520 -320 -1856 -320
WIRE -1456 -320 -1520 -320
WIRE -1024 -320 -1456 -320
WIRE -832 -288 -880 -288
WIRE -688 -288 -832 -288
WIRE -608 -288 -688 -288
WIRE -480 -288 -528 -288
WIRE -368 -288 -480 -288
WIRE -128 -288 -288 -288
WIRE 112 -288 -128 -288
WIRE 480 -288 192 -288
WIRE 592 -288 480 -288
WIRE 864 -288 592 -288
WIRE 1008 -288 944 -288
WIRE 1600 -288 1008 -288
WIRE 1664 -288 1600 -288
WIRE -1024 -256 -1104 -256
WIRE -992 -192 -992 -208
WIRE -480 -176 -480 -288
WIRE 1008 -176 1008 -288
WIRE 80 -160 80 -176
WIRE 144 -160 144 -176
WIRE -1856 -144 -1856 -320
WIRE -1104 -80 -1104 -256
WIRE -992 -80 -1104 -80
WIRE -832 -80 -832 -288
WIRE -832 -80 -912 -80
WIRE -1104 -64 -1104 -80
WIRE -128 -64 -128 -288
WIRE 32 -64 -128 -64
WIRE -1456 -48 -1456 -320
WIRE 480 -48 480 -288
WIRE 480 -48 336 -48
WIRE 32 -16 0 -16
WIRE -1856 0 -1856 -64
WIRE -1856 0 -1984 0
WIRE -480 0 -480 -112
WIRE -416 0 -480 0
WIRE 1008 0 1008 -112
WIRE 1072 0 1008 0
WIRE -416 16 -416 0
WIRE 480 16 336 16
WIRE 1072 16 1072 0
WIRE -1984 32 -1984 0
WIRE 32 32 -128 32
WIRE -1856 48 -1856 0
WIRE -1104 48 -1104 16
WIRE -992 48 -1104 48
WIRE -832 48 -912 48
WIRE -480 80 -480 0
WIRE 1008 80 1008 0
WIRE 144 144 144 128
WIRE -992 176 -992 160
WIRE -1104 224 -1104 48
WIRE -1024 224 -1104 224
WIRE -832 256 -832 48
WIRE -832 256 -880 256
WIRE -688 256 -832 256
WIRE -608 256 -688 256
WIRE -480 256 -480 144
WIRE -480 256 -528 256
WIRE -368 256 -480 256
WIRE -128 256 -128 32
WIRE -128 256 -288 256
WIRE 96 256 -128 256
WIRE 480 256 480 16
WIRE 480 256 176 256
WIRE 592 256 480 256
WIRE 864 256 592 256
WIRE 1008 256 1008 144
WIRE 1008 256 944 256
WIRE 1600 256 1008 256
WIRE 1664 256 1600 256
WIRE -1856 288 -1856 128
WIRE -1520 288 -1856 288
WIRE -1456 288 -1456 32
WIRE -1456 288 -1520 288
WIRE -1024 288 -1456 288
WIRE 1760 288 1760 272
WIRE 1872 288 1872 272
WIRE 1984 288 1984 272
WIRE -992 352 -992 336
WIRE -944 352 -944 336
WIRE 1760 384 1760 368
WIRE 1872 384 1872 368
WIRE 1984 384 1984 368
FLAG 1760 384 0
FLAG 1760 272 Vcc
IOPIN 2400 400 In
FLAG 1872 384 0
FLAG 1872 272 Vss
IOPIN 2512 400 In
FLAG 1984 384 0
FLAG 1984 272 Vcm
IOPIN 2624 400 In
FLAG -1520 -320 Vi_P
FLAG -1520 288 Vi_N
FLAG 592 -288 Vo_P
FLAG 592 256 Vo_N
FLAG -992 -384 Vss
IOPIN -352 -256 In
FLAG -992 -192 Vcc
IOPIN -352 -64 In
FLAG -1984 32 0
FLAG 1600 -288 V_fltr_P
FLAG 1600 256 V_fltr_N
FLAG -992 352 Vss
IOPIN -352 480 In
FLAG -992 160 Vcc
IOPIN -352 288 In
FLAG -688 -288 V_amp_P
FLAG -688 256 V_amp_N
FLAG -416 16 0
FLAG 1072 16 0
FLAG -944 -384 Vcc
IOPIN -304 -256 In
FLAG -944 352 Vcc
IOPIN -304 480 In
FLAG 0 -16 Vcm
IOPIN 640 112 In
FLAG 144 144 Vss
IOPIN 784 272 In
FLAG 144 -176 Vcc
IOPIN 784 -48 In
FLAG 80 -176 Vcc
IOPIN 720 -48 In
SYMBOL voltage -1856 -160 R0
SYMATTR Value2 AC 1
SYMATTR InstName V1
SYMATTR Value SINE(0 5m 10k)
SYMBOL voltage 1760 272 R0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL voltage 1872 272 R0
SYMATTR InstName V3
SYMATTR Value -5
SYMBOL voltage 1984 272 R0
SYMATTR InstName V4
SYMATTR Value 2.048
SYMBOL res -1120 -80 R0
SYMATTR InstName R5
SYMATTR Value {R1} noiseless
SYMBOL res -896 -96 R90
SYMATTR InstName R6
SYMATTR Value {R2} noiseless
SYMBOL res -896 32 R90
SYMATTR InstName R12
SYMATTR Value {R2} noiseless
SYMBOL voltage -1856 32 R0
SYMATTR InstName V5
SYMATTR Value SINE(0 5m 10k)
SYMBOL res -512 -304 R90
SYMATTR InstName R7
SYMATTR Value {R_flt} noiseless
SYMBOL res -512 240 R90
SYMATTR InstName R8
SYMATTR Value {R_flt} noiseless
SYMBOL res 960 -304 R90
SYMATTR InstName R9
SYMATTR Value {R_flt}
SYMBOL res 960 240 R90
SYMATTR InstName R10
SYMATTR Value {R_flt}
SYMBOL cap -496 -176 R0
SYMATTR InstName C1
SYMATTR Value {C_flt} noiseless
SYMBOL cap -496 80 R0
SYMATTR InstName C2
SYMATTR Value {C_flt} noiseless
SYMBOL cap 992 -176 R0
SYMATTR InstName C3
SYMATTR Value {C_flt}
SYMBOL cap 992 80 R0
SYMATTR InstName C4
SYMATTR Value {C_flt}
SYMBOL OpAmps\\LTC6228 -992 -288 M180
SYMATTR InstName U1
SYMBOL OpAmps\\LTC6228 -992 256 R0
SYMATTR InstName U2
SYMBOL res -272 -304 R90
SYMATTR InstName R1
SYMATTR Value 250
SYMBOL res -272 240 R90
SYMATTR InstName R2
SYMATTR Value 250
SYMBOL res 208 -304 R90
SYMATTR InstName R3
SYMATTR Value 5000
SYMBOL res 192 240 R90
SYMATTR InstName R4
SYMATTR Value 5000
SYMBOL OpAmps\\LTC6404-1 160 -16 R0
SYMATTR InstName U4