* SPICE netlist
V1 +3.3V 0 3.3
XU1 N001 vGND +3.3V 0 vGND level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
R1 +3.3V N001 33k
R2 N001 0 33k
VU U_e vGND AC 1.5
R5 N004 U_e 16k
C1 U_TP N004 10n
C4 vGND N005 10n
R4 N005 N004 16k
XTP N005 U_TP +3.3V 0 U_TP level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
C2 U_e N003 10n
C3 N003 N002 10n
R6 U_HP N003 16k
XHP N002 U_HP +3.3V 0 U_HP level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
R7 N002 vGND 16k
XAdd vGND N006 +3.3V 0 U_a level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
R8 P001 U_HP {R2}
R9 P002 N008 {R1}
R10 U_a N006 10k
XInv vGND N007 +3.3V 0 N008 level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
R11 N008 N007 220k
R12 N007 U_TP 220k
R3 N006 P001 10k
R13 N006 P002 10k
.ac oct 10000 100 10k
.step param R1 list 10k 90k
.step param R2 list 90k 10k

* LTspice schematic (.asc)
Version 4
SHEET 1 1488 2192
WIRE -600 -1064 -600 -1096
WIRE -456 -1064 -600 -1064
WIRE -456 -1032 -456 -1064
WIRE -216 -1032 -392 -1032
WIRE -600 -920 -600 -1064
WIRE -392 -904 -392 -1032
WIRE -360 -904 -392 -904
WIRE -216 -888 -216 -1032
WIRE -216 -888 -296 -888
WIRE -184 -888 -216 -888
WIRE -456 -872 -456 -952
WIRE -360 -872 -456 -872
WIRE -456 -824 -456 -872
WIRE -328 -824 -328 -856
WIRE -600 -680 -600 -840
WIRE -456 -680 -456 -744
WIRE -456 -680 -600 -680
WIRE -600 -664 -600 -680
WIRE -472 264 -680 264
WIRE -200 264 -472 264
WIRE 520 264 312 264
WIRE 744 264 520 264
WIRE -200 280 -200 264
WIRE 312 280 312 264
WIRE -472 376 -472 264
WIRE -472 376 -536 376
WIRE 520 376 520 264
WIRE 600 376 520 376
WIRE -680 392 -680 264
WIRE -680 392 -744 392
WIRE -600 392 -680 392
WIRE 744 392 744 264
WIRE 744 392 664 392
WIRE -408 408 -536 408
WIRE -344 408 -408 408
WIRE -200 408 -200 360
WIRE -200 408 -280 408
WIRE -136 408 -200 408
WIRE -72 408 -88 408
WIRE -8 408 -72 408
WIRE 120 408 -8 408
WIRE 312 408 312 344
WIRE 312 408 200 408
WIRE 376 408 312 408
WIRE 520 408 456 408
WIRE 600 408 520 408
WIRE 632 456 632 424
WIRE -408 472 -408 408
WIRE -8 488 -8 408
WIRE 520 488 520 408
WIRE 520 568 520 552
WIRE 88 824 40 824
WIRE 216 824 168 824
WIRE -440 872 -504 872
WIRE -280 872 -360 872
WIRE -8 968 -8 936
WIRE 40 968 40 824
WIRE 40 968 -8 968
WIRE 88 968 40 968
WIRE 216 984 216 824
WIRE 216 984 152 984
WIRE 88 1000 40 1000
WIRE -648 1016 -680 1016
WIRE -504 1016 -504 872
WIRE -504 1016 -568 1016
WIRE -440 1016 -504 1016
WIRE -280 1032 -280 872
WIRE -280 1032 -376 1032
WIRE -168 1032 -280 1032
WIRE -8 1032 -8 968
WIRE -440 1048 -472 1048
WIRE 40 1080 40 1000
WIRE -472 1096 -472 1048
FLAG -328 -824 0
FLAG -328 -920 +3.3V
IOPIN 336 128 In
FLAG -600 -1096 +3.3V
IOPIN 64 -48 Out
FLAG -600 -664 0
FLAG -184 -888 vGND
IOPIN 480 160 Out
FLAG 632 456 0
FLAG -8 568 vGND
IOPIN 656 1616 In
FLAG 520 568 vGND
IOPIN 1184 1616 In
FLAG 632 360 +3.3V
IOPIN 1296 1408 In
FLAG -8 408 U_e
FLAG -568 360 +3.3V
IOPIN 96 1408 In
FLAG -568 424 0
FLAG -408 552 vGND
IOPIN 256 1600 In
FLAG -744 392 U_HP
IOPIN -80 1440 Out
FLAG 744 392 U_TP
IOPIN 1408 1440 Out
FLAG -168 936 U_HP
IOPIN 496 1984 In
FLAG -680 1016 U_TP
IOPIN -16 2064 In
FLAG 120 952 +3.3V
IOPIN 784 2000 In
FLAG 120 1016 0
FLAG 216 984 U_a
FLAG 40 1080 vGND
IOPIN 704 2128 In
FLAG -408 1000 +3.3V
IOPIN 256 2048 In
FLAG -408 1064 0
FLAG -472 1096 vGND
IOPIN 192 2144 In
SYMBOL voltage -600 -936 R0
SYMATTR InstName V1
SYMATTR Value 3.3
SYMBOL OpAmps\\UniversalOpAmp2 -328 -888 R0
SYMATTR InstName U1
SYMBOL res -472 -1048 R0
SYMATTR InstName R1
SYMATTR Value 33k
SYMBOL res -472 -840 R0
SYMATTR InstName R2
SYMATTR Value 33k
SYMBOL voltage -8 472 R0
SYMATTR Value2 AC 1.5
SYMATTR InstName U
SYMATTR Value ""
SYMBOL res 216 392 R90
SYMATTR InstName R5
SYMATTR Value 16k
SYMBOL cap 296 280 R0
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL cap 536 552 R180
SYMATTR InstName C4
SYMATTR Value 10n
SYMBOL res 472 392 R90
SYMATTR InstName R4
SYMATTR Value 16k
SYMBOL OpAmps\\UniversalOpAmp2 632 392 R0
SYMATTR InstName TP
SYMBOL cap -72 392 R90
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL cap -280 392 R90
SYMATTR InstName C3
SYMATTR Value 10n
SYMBOL res -216 264 R0
SYMATTR InstName R6
SYMATTR Value 16k
SYMBOL OpAmps\\UniversalOpAmp2 -568 392 M0
SYMATTR InstName HP
SYMBOL res -424 456 R0
SYMATTR InstName R7
SYMATTR Value 16k
SYMBOL OpAmps\\UniversalOpAmp2 120 984 R0
SYMATTR InstName Add
SYMBOL res -72 920 R90
SYMATTR InstName R8
SYMATTR Value {R2}
SYMBOL res -72 1016 R90
SYMATTR InstName R9
SYMATTR Value {R1}
SYMBOL res 184 808 R90
SYMATTR InstName R10
SYMATTR Value 10k
SYMBOL OpAmps\\UniversalOpAmp2 -408 1032 R0
SYMATTR InstName Inv
SYMBOL res -344 856 R90
SYMATTR InstName R11
SYMATTR Value 220k
SYMBOL res -552 1000 R90
SYMATTR InstName R12
SYMATTR Value 220k
SYMBOL res 8 920 R90
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL res 8 1016 R90
SYMATTR InstName R13
SYMATTR Value 10k