* SPICE netlist
XU1 N006 N004 N002 Vcc 0 LTC2054 ;pnba IN+)IN-)OUT)VCC)VEE
XU2 N003 N002 N005 Vcc 0 LTC2054 ;pnba IN+)IN-)OUT)VCC)VEE
R1 Vcc N003 10k
R2 N003 0 1k
V1 Vcc 0 3.3
C1 N004 N002 {C_Int}
R3 N004 0 {R_f}
R4 N005 0 10k
V2 Pulse 0 PULSE(0 3.3 10e-4 1e-9 1e-9 10e-3 20e-3 1)
V3 -Vcc 0 -3.3
R5 N006 Pulse {R_f}
C2 N006 0 {C_Int}
M1 N002 N001 N004 N004 2N7002
M2 N001 Pulse 0 0 2N7002
M3 N001 Pulse Vcc Vcc FDC638P
XU3 N012 N010 N008 Vcc 0 LTC2054 ;pnba IN+)IN-)OUT)VCC)VEE
XU4 N009 N008 N011 Vcc 0 LTC2054 ;pnba IN+)IN-)OUT)VCC)VEE
R6 Vcc N009 10k
R7 N009 0 20k
C3 N010 N008 {C_Int}
R8 N010 0 {R_f}
R9 N011 0 10k
R10 N012 Pulse {R_f}
C4 N012 0 {C_Int}
M4 N008 N007 N010 N010 IRF6201
M5 N007 Pulse 0 0 2N7002
M6 N007 Pulse Vcc Vcc FDC638P
.tran 200e-3
.param R_f = 10k
.param C_Int = 1u

* LTspice schematic (.asc)
Version 4
SHEET 1 1168 1280
WIRE -72 -640 -584 -640
WIRE -72 -608 -72 -640
WIRE 24 -560 8 -560
WIRE 56 -560 56 -576
WIRE 56 -464 56 -480
WIRE 120 -464 56 -464
WIRE -88 -432 -88 -560
WIRE -56 -432 -88 -432
WIRE 24 -432 24 -560
WIRE 24 -432 8 -432
WIRE 56 -368 56 -384
WIRE 24 -336 24 -432
WIRE 40 -336 24 -336
WIRE 120 -336 120 -464
WIRE 120 -336 88 -336
WIRE -456 -320 -456 -336
WIRE 168 -320 168 -352
WIRE -376 -304 -408 -304
WIRE -8 -304 -8 -336
WIRE 136 -304 56 -304
WIRE -184 -288 -248 -288
WIRE -88 -288 -88 -432
WIRE -88 -288 -104 -288
WIRE -40 -288 -88 -288
WIRE 312 -288 200 -288
WIRE -248 -272 -248 -288
WIRE 40 -272 40 -336
WIRE 40 -272 24 -272
WIRE 56 -272 56 -304
WIRE 56 -272 40 -272
WIRE 88 -272 88 -336
WIRE 136 -272 88 -272
WIRE -40 -256 -88 -256
WIRE 168 -224 168 -256
WIRE -584 -208 -584 -640
WIRE -456 -208 -456 -224
WIRE -456 -208 -584 -208
WIRE -376 -208 -376 -304
WIRE -280 -208 -376 -208
WIRE -184 -208 -280 -208
WIRE -88 -208 -88 -256
WIRE -88 -208 -104 -208
WIRE -8 -208 -8 -240
WIRE -456 -192 -456 -208
WIRE -280 -192 -280 -208
WIRE -88 -192 -88 -208
WIRE 312 -176 312 -208
WIRE 456 -176 456 -208
WIRE 584 -176 584 -208
WIRE -376 -112 -376 -208
WIRE -376 -112 -408 -112
WIRE -88 -96 -88 -128
WIRE -456 -64 -456 -96
WIRE -280 -64 -280 -112
WIRE 456 -64 456 -96
WIRE 584 -64 584 -96
WIRE -72 64 -584 64
WIRE -72 96 -72 64
WIRE 24 144 8 144
WIRE 56 144 56 128
WIRE 56 240 56 224
WIRE 120 240 56 240
WIRE -88 272 -88 144
WIRE -56 272 -88 272
WIRE 24 272 24 144
WIRE 24 272 8 272
WIRE 56 336 56 320
WIRE 24 368 24 272
WIRE 40 368 24 368
WIRE 120 368 120 240
WIRE 120 368 88 368
WIRE -456 384 -456 368
WIRE 168 384 168 352
WIRE -376 400 -408 400
WIRE -8 400 -8 368
WIRE 136 400 56 400
WIRE -184 416 -248 416
WIRE -88 416 -88 272
WIRE -88 416 -104 416
WIRE -40 416 -88 416
WIRE 312 416 200 416
WIRE -248 432 -248 416
WIRE 40 432 40 368
WIRE 40 432 24 432
WIRE 56 432 56 400
WIRE 56 432 40 432
WIRE 88 432 88 368
WIRE 136 432 88 432
WIRE -40 448 -88 448
WIRE 168 480 168 448
WIRE -584 496 -584 64
WIRE -456 496 -456 480
WIRE -456 496 -584 496
WIRE -376 496 -376 400
WIRE -280 496 -376 496
WIRE -184 496 -280 496
WIRE -88 496 -88 448
WIRE -88 496 -104 496
WIRE -8 496 -8 464
WIRE -456 512 -456 496
WIRE -280 512 -280 496
WIRE -88 512 -88 496
WIRE 312 528 312 496
WIRE -376 592 -376 496
WIRE -376 592 -408 592
WIRE -88 608 -88 576
WIRE -456 640 -456 608
FLAG 456 -208 Vcc
FLAG 456 -64 0
FLAG -8 -336 Vcc
FLAG 168 -352 Vcc
FLAG 56 -368 0
FLAG 56 -576 Vcc
FLAG 312 -176 0
FLAG -280 -64 0
FLAG 584 -64 0
FLAG 584 -208 -Vcc
FLAG -248 -272 0
FLAG -88 -96 0
FLAG 168 -224 0
FLAG -8 -208 0
FLAG -456 -64 0
FLAG -456 -336 Vcc
FLAG -8 368 Vcc
FLAG 168 352 Vcc
FLAG 56 336 0
FLAG 56 128 Vcc
FLAG 312 528 0
FLAG -248 432 0
FLAG -88 608 0
FLAG 168 480 0
FLAG -8 496 0
FLAG -456 640 0
FLAG -456 368 Vcc
FLAG -280 -208 Pulse
FLAG -280 496 Pulse
SYMBOL Opamps\\LTC2054 -8 -272 R0
SYMATTR InstName U1
SYMBOL Opamps\\LTC2054 168 -288 R0
SYMATTR InstName U2
SYMBOL res 40 -576 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res 40 -480 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL voltage 456 -192 R0
SYMATTR InstName V1
SYMATTR Value 3.3
SYMBOL cap -56 -448 M90
SYMATTR InstName C1
SYMATTR Value {C_Int}
SYMBOL res -88 -304 R90
SYMATTR InstName R3
SYMATTR Value {R_f}
SYMBOL res 296 -304 R0
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL voltage -280 -208 R0
SYMATTR InstName V2
SYMATTR Value PULSE(0 3.3 10e-4 1e-9 1e-9 10e-3 20e-3 1)
SYMBOL voltage 584 -192 R0
SYMATTR InstName V3
SYMATTR Value -3.3
SYMBOL res -88 -224 R90
SYMATTR InstName R5
SYMATTR Value {R_f}
SYMBOL cap -104 -192 R0
SYMATTR InstName C2
SYMATTR Value {C_Int}
SYMBOL nmos 8 -608 R90
SYMATTR InstName M1
SYMATTR Value 2N7002
SYMBOL nmos -408 -192 M0
SYMATTR InstName M2
SYMATTR Value 2N7002
SYMBOL pmos -408 -224 R180
SYMATTR InstName M3
SYMATTR Value FDC638P
SYMBOL Opamps\\LTC2054 -8 432 R0
SYMATTR InstName U3
SYMBOL Opamps\\LTC2054 168 416 R0
SYMATTR InstName U4
SYMBOL res 40 128 R0
SYMATTR InstName R6
SYMATTR Value 10k
SYMBOL res 40 224 R0
SYMATTR InstName R7
SYMATTR Value 20k
SYMBOL cap -56 256 M90
SYMATTR InstName C3
SYMATTR Value {C_Int}
SYMBOL res -88 400 R90
SYMATTR InstName R8
SYMATTR Value {R_f}
SYMBOL res 296 400 R0
SYMATTR InstName R9
SYMATTR Value 10k
SYMBOL res -88 480 R90
SYMATTR InstName R10
SYMATTR Value {R_f}
SYMBOL cap -104 512 R0
SYMATTR InstName C4
SYMATTR Value {C_Int}
SYMBOL nmos 8 96 R90
SYMATTR InstName M4
SYMATTR Value IRF6201
SYMBOL nmos -408 512 M0
SYMATTR InstName M5
SYMATTR Value 2N7002
SYMBOL pmos -408 480 R180
SYMATTR InstName M6
SYMATTR Value FDC638P