* SPICE netlist
V1 Vcc 0 5
VCarrier Vcarrier 0 SINE(0 1 1k 0 0 0)
R1 N003 Vcarrier 1k
Q1 N006 N009 0 0 2N3904
Vsignal Vsignal_send 0 PULSE(0 5 5m 1n 1n 5m 10m 3)
V4 Vee 0 -5
R2 N009 N008 1k
R3 0 N002 20k
C1 0 N002 100n
Rx1 N005 Vcc 10k
Ry1 N005 0 222
Rh1 N004 N005 2.5k
XU4 N005 N002 Vcc 0 N004 LT1720 ;pnba In+)In-)V+)V-)OUT
XU3 N007 N004 Vcc 0 Vreceived LT1720 ;pnba In+)In-)V+)V-)OUT
R4 N007 Vcc 10k
R5 0 N007 2k
R6 Vreceived 0 1k
XU5 N003 Vant Vcc Vee N001 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
D1 Vant N002 1N5818
R7 N003 N006 0.5k
Q2 N008 N010 0 0 2N3904
R8 N010 Vsignal_send 1k
R9 N008 Vcc 1k
Q3 N003 N012 0 0 2N3904
R13 N012 N011 1k
Q5 Vcc N001 Vant 0 2N3904
Q6 Vant N001 Vee 0 2N3906
V2 N011 0 PULSE(0 5 30m 1n 1n 10s)
XU2 N002 N013 Vcc 0 N014 LT1720 ;pnba In+)In-)V+)V-)OUT
R11 N013 Vcc 9.2k
R12 0 N013 0.1k
R14 N014 0 10k
C2 N014 0 10n
.tran 0 40m 0

* LTspice schematic (.asc)
Version 4
SHEET 1 3552 1024
WIRE -320 -512 -848 -512
WIRE -944 -448 -1232 -448
WIRE -1776 -416 -1776 -448
WIRE -1664 -416 -1664 -448
WIRE -1232 -416 -1232 -448
WIRE -944 -416 -944 -448
WIRE -432 -416 -432 -448
WIRE -496 -368 -672 -368
WIRE -1776 -320 -1776 -336
WIRE -1664 -320 -1664 -336
WIRE -768 -320 -768 -336
WIRE -1232 -304 -1232 -336
WIRE -848 -304 -848 -512
WIRE -800 -304 -848 -304
WIRE 1040 -304 1040 -336
WIRE -672 -288 -672 -368
WIRE -672 -288 -736 -288
WIRE -432 -288 -432 -320
WIRE -320 -288 -320 -512
WIRE -320 -288 -432 -288
WIRE -224 -288 -320 -288
WIRE 432 -288 -224 -288
WIRE 576 -288 496 -288
WIRE 672 -288 576 -288
WIRE 704 -288 672 -288
WIRE 1008 -288 704 -288
WIRE -944 -272 -944 -336
WIRE -848 -272 -944 -272
WIRE -800 -272 -848 -272
WIRE 1200 -272 1072 -272
WIRE -432 -256 -432 -288
WIRE 672 -256 672 -288
WIRE 1008 -256 960 -256
WIRE 576 -240 576 -288
WIRE -944 -224 -944 -272
WIRE -768 -224 -768 -256
WIRE -672 -208 -672 -288
WIRE -496 -208 -672 -208
WIRE 1040 -192 1040 -240
WIRE -1312 -176 -1312 -208
WIRE 576 -144 576 -176
WIRE 672 -144 672 -176
WIRE -432 -128 -432 -160
WIRE 1520 -128 1520 -160
WIRE 816 -112 768 -112
WIRE 960 -112 960 -256
WIRE 960 -112 896 -112
WIRE 1072 -112 960 -112
WIRE 1200 -112 1200 -272
WIRE 1200 -112 1152 -112
WIRE 1488 -112 1200 -112
WIRE -944 -96 -944 -144
WIRE 1776 -96 1552 -96
WIRE 960 -80 960 -112
WIRE 1488 -80 1440 -80
WIRE 1776 -80 1776 -96
WIRE -1312 -48 -1312 -96
WIRE -1200 -48 -1312 -48
WIRE -1008 -48 -1120 -48
WIRE 1312 -32 1264 -32
WIRE 1440 -32 1440 -80
WIRE 1440 -32 1392 -32
WIRE -1312 -16 -1312 -48
WIRE 1520 -16 1520 -64
WIRE -1552 32 -1744 32
WIRE -1376 32 -1472 32
WIRE -944 32 -944 0
WIRE 960 32 960 0
WIRE 1440 32 1440 -32
WIRE 1776 32 1776 0
WIRE -1744 112 -1744 32
WIRE -1312 128 -1312 80
WIRE -848 144 -848 -272
WIRE 1440 144 1440 112
WIRE -1040 192 -1168 192
WIRE -912 192 -960 192
WIRE 736 208 736 144
WIRE 960 208 816 208
WIRE 1104 208 1040 208
WIRE -1168 224 -1168 192
WIRE -1744 240 -1744 192
WIRE 1104 256 1104 208
WIRE -848 272 -848 240
WIRE -1168 320 -1168 304
WIRE 864 336 864 304
WIRE 816 352 816 208
WIRE 832 352 816 352
WIRE 1200 368 896 368
WIRE 1296 368 1200 368
WIRE 1536 368 1296 368
WIRE 704 384 704 -288
WIRE 832 384 704 384
WIRE 1200 384 1200 368
WIRE 1296 400 1296 368
WIRE 864 448 864 400
WIRE 1200 512 1200 464
WIRE 1296 512 1296 464
FLAG -1744 240 0
FLAG -1232 -304 0
FLAG -944 32 0
FLAG -1776 -320 0
FLAG -1776 -448 Vcc
FLAG -1664 -320 0
FLAG -1664 -448 Vee
FLAG 672 -144 0
FLAG 1040 -336 Vcc
FLAG 960 32 0
FLAG 1040 -192 0
FLAG 768 -112 Vcc
FLAG 1520 -160 Vcc
FLAG 1520 -16 0
FLAG 1440 144 0
FLAG 1264 -32 Vcc
FLAG 1776 32 0
FLAG -768 -336 Vcc
FLAG -768 -224 Vee
FLAG 576 -144 0
FLAG 1776 -96 Vreceived
FLAG -224 -288 Vant
FLAG -1312 -208 Vcc
FLAG -1312 128 0
FLAG -848 272 0
FLAG -1744 32 Vsignal_send
FLAG -1232 -448 Vcarrier
FLAG -432 -128 Vee
FLAG -432 -448 Vcc
FLAG -1168 320 0
FLAG 864 304 Vcc
FLAG 864 448 0
FLAG 736 144 Vcc
FLAG 1104 256 0
FLAG 1200 512 0
FLAG 1296 512 0
SYMBOL voltage -1776 -432 R0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL voltage -1232 -432 R0
SYMATTR InstName Carrier
SYMATTR Value SINE(0 1 1k 0 0 0)
SYMBOL res -928 -320 R180
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL npn -1008 -96 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL voltage -1744 96 R0
SYMATTR InstName Vsignal
SYMATTR Value PULSE(0 5 5m 1n 1n 5m 10m 3)
SYMBOL voltage -1664 -432 R0
SYMATTR InstName V4
SYMATTR Value -5
SYMBOL res -1104 -64 R90
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL res 688 -160 R180
SYMATTR InstName R3
SYMATTR Value 20k
SYMBOL cap 592 -176 R180
SYMATTR InstName C1
SYMATTR Value 100n
SYMBOL res 912 -128 R90
SYMATTR InstName Rx1
SYMATTR Value 10k
SYMBOL res 944 -96 R0
SYMATTR InstName Ry1
SYMATTR Value 222
SYMBOL res 1168 -128 R90
SYMATTR InstName Rh1
SYMATTR Value 2.5k
SYMBOL Comparators\\LT1720 1040 -336 R0
SYMATTR InstName U4
SYMBOL Comparators\\LT1720 1520 -160 R0
SYMATTR InstName U3
SYMBOL res 1408 -48 R90
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL res 1456 128 R180
SYMATTR InstName R5
SYMATTR Value 2k
SYMBOL res 1760 -96 R0
SYMATTR InstName R6
SYMATTR Value 1k
SYMBOL Opamps\\UniversalOpamp2 -768 -288 R0
SYMATTR InstName U5
SYMBOL schottky 432 -272 R270
SYMATTR InstName D1
SYMATTR Value 1N5818
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res -960 -240 R0
SYMATTR InstName R7
SYMATTR Value 0.5k
SYMBOL npn -1376 -16 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res -1456 16 R90
SYMATTR InstName R8
SYMATTR Value 1k
SYMBOL res -1296 -80 R180
SYMATTR InstName R9
SYMATTR Value 1k
SYMBOL npn -912 144 R0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res -944 176 R90
SYMATTR InstName R13
SYMATTR Value 1k
SYMBOL npn -496 -416 R0
SYMATTR InstName Q5
SYMATTR Value 2N3904
SYMBOL pnp -496 -256 R0
SYMATTR InstName Q6
SYMATTR Value 2N3906
SYMBOL voltage -1168 208 R0
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 30m 1n 1n 10s)
SYMBOL Comparators\\LT1720 864 304 R0
SYMATTR InstName U2
SYMBOL res 832 192 R90
SYMATTR InstName R11
SYMATTR Value 9.2k
SYMBOL res 1056 192 R90
SYMATTR InstName R12
SYMATTR Value 0.1k
SYMBOL res 1184 368 R0
SYMATTR InstName R14
SYMATTR Value 10k
SYMBOL cap 1280 400 R0
SYMATTR InstName C2
SYMATTR Value 10n