* SPICE netlist
V1 in 0 SINE(1.65 1.65 2000) Rser=1
V3 N002 0 12 Rser=1
R3 N002 N005 1k
R4 N005 0 1k
R1 in_sum N006 680
XU1 0 N006 N002 0 in_sum LT1497 ;pnba In+)In-)V+)V-)OUT
L1 out ref 7m Rser=30
XU2 N011 N010 N002 0 out LT1497 ;pnba In+)In-)V+)V-)OUT
L2 N004 ref 7m Rser=70
R7 N006 0 680
R2 in_sum_scale ref 10k
R8 in_sum_scale in 10k
R5 N011 ref 100k
C1 in_sum_scale N011 10n
R6 out N010 1000
R9 N010 ref 470
XU3 N005 ref N002 0 ref LT1497 ;pnba In+)In-)V+)V-)OUT
C2 in_sum N006 100n
R10 N004 N009 10k
R11 N009 0 4k7
V2 N001 0 PULSE(-25 25 0 0 0 0 0.00005) Rser=1
C3 N001 N003 1n
XU4 0 N007 N002 0 sig LT1497 ;pnba In+)In-)V+)V-)OUT
R12 sig N007 680
R13 N007 N009 680
C4 sig N007 100n
D1 N012 ref 1N750
D2 ref N012 1N750
C5 out N008 100n
.tran 0 5mS
K1 L1 L2 0.5

* LTspice schematic (.asc)
Version 4
SHEET 1 2432 512
WIRE 336 -256 -1216 -256
WIRE -1216 -240 -1216 -256
WIRE 336 -224 336 -256
WIRE -1040 -112 -1136 -112
WIRE -896 -112 -1040 -112
WIRE -192 -112 -896 -112
WIRE 192 -112 -192 -112
WIRE 1088 -112 192 -112
WIRE -304 -80 -384 -80
WIRE -128 -80 -304 -80
WIRE -1040 -64 -1040 -112
WIRE -864 -64 -944 -64
WIRE -832 -64 -864 -64
WIRE 80 -64 0 -64
WIRE 256 -64 80 -64
WIRE 336 -64 336 -160
WIRE 640 -64 464 -64
WIRE 928 -64 832 -64
WIRE 1152 -64 928 -64
WIRE -128 -48 -128 -80
WIRE -896 -32 -896 -112
WIRE -576 -32 -672 -32
WIRE -448 -32 -576 -32
WIRE -1136 -16 -1136 -112
WIRE -944 -16 -944 -64
WIRE -928 -16 -944 -16
WIRE -832 0 -832 -64
WIRE -832 0 -864 0
WIRE -736 0 -832 0
WIRE -192 0 -192 -112
WIRE 1088 0 1088 -112
WIRE -928 16 -1040 16
WIRE -384 16 -384 -16
WIRE -304 16 -304 0
WIRE -304 16 -384 16
WIRE -224 16 -304 16
WIRE 832 16 832 0
WIRE 928 16 832 16
WIRE 1056 16 928 16
WIRE -128 32 -128 -48
WIRE -128 32 -160 32
WIRE -64 32 -112 32
WIRE 0 32 0 0
WIRE 1152 32 1152 -64
WIRE 1152 32 1120 32
WIRE 1216 32 1152 32
WIRE -736 48 -736 0
WIRE -672 48 -736 48
WIRE -224 48 -240 48
WIRE 192 48 192 -112
WIRE 640 48 640 16
WIRE 720 48 640 48
WIRE 832 48 832 16
WIRE 832 48 800 48
WIRE 1056 48 1040 48
WIRE -304 64 -304 16
WIRE 80 64 80 16
WIRE 160 64 80 64
WIRE 640 64 640 48
WIRE 256 80 256 -64
WIRE 256 80 224 80
WIRE 288 80 256 80
WIRE 352 80 288 80
WIRE 160 96 -64 96
WIRE -576 128 -576 112
WIRE -1216 144 -1216 -160
WIRE -1136 144 -1136 64
WIRE -1136 144 -1216 144
WIRE -1040 144 -1040 96
WIRE -1040 144 -1136 144
WIRE -896 144 -896 32
WIRE -896 144 -1040 144
WIRE -576 144 -576 128
WIRE -576 144 -896 144
WIRE -304 144 -576 144
WIRE -240 144 -240 48
WIRE -240 144 -304 144
WIRE -192 144 -192 64
WIRE -192 144 -240 144
WIRE 192 144 192 112
WIRE 192 144 -192 144
WIRE 640 144 192 144
WIRE 1040 144 1040 48
WIRE 1040 144 640 144
WIRE 1088 144 1088 64
WIRE 1088 144 1040 144
WIRE -1136 160 -1136 144
WIRE -64 176 -64 96
WIRE 80 176 80 64
WIRE 352 176 352 80
WIRE 464 176 464 -64
WIRE 656 176 576 176
WIRE -448 192 -448 -32
WIRE -112 192 -448 192
WIRE -112 192 -112 32
WIRE 576 192 576 176
WIRE 656 192 656 176
WIRE -736 256 -736 48
WIRE -64 256 -736 256
WIRE 80 256 -64 256
WIRE 352 256 80 256
WIRE 464 256 352 256
WIRE 576 256 464 256
WIRE 656 256 576 256
FLAG -1136 160 0
FLAG -864 -64 ref
FLAG -576 -32 in_sum_scale
FLAG -576 48 in
FLAG -128 -48 in_sum
FLAG 288 80 out
FLAG 1216 32 sig
SYMBOL voltage -576 32 R0
SYMATTR InstName V1
SYMATTR Value SINE(1.65 1.65 2000)
SYMATTR SpiceLine Rser=1
SYMBOL voltage -1136 -32 R0
SYMATTR InstName V3
SYMATTR Value 12
SYMATTR SpiceLine Rser=1
SYMBOL res -1056 -80 R0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL res -1056 0 R0
SYMATTR InstName R4
SYMATTR Value 1k
SYMBOL res -320 -96 R0
SYMATTR InstName R1
SYMATTR Value 680
SYMBOL Opamps/LT1497 -192 -32 R0
SYMATTR InstName U1
SYMBOL ind2 336 160 R0
SYMATTR InstName L1
SYMATTR Value 7m
SYMATTR Type ind
SYMATTR SpiceLine Rser=30
SYMBOL Opamps/LT1497 192 16 R0
SYMATTR InstName U2
SYMBOL ind2 448 160 R0
SYMATTR InstName L2
SYMATTR Value 7m
SYMATTR SpiceLine Rser=70
SYMBOL res -320 48 R0
SYMATTR InstName R7
SYMATTR Value 680
SYMBOL res -688 -48 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res -592 -48 R0
SYMATTR InstName R8
SYMATTR Value 10k
SYMBOL res -80 160 R0
SYMATTR InstName R5
SYMATTR Value 100k
SYMBOL cap -80 32 R0
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL res 64 -80 R0
SYMATTR InstName R6
SYMATTR Value 1000
SYMBOL res 64 160 R0
SYMATTR InstName R9
SYMATTR Value 470
SYMBOL Opamps/LT1497 -896 -64 R0
SYMATTR InstName U3
SYMBOL cap -400 -80 R0
SYMATTR InstName C2
SYMATTR Value 100n
SYMBOL res 624 -80 R0
SYMATTR InstName R10
SYMATTR Value 10k
SYMBOL res 624 48 R0
SYMATTR InstName R11
SYMATTR Value 4k7
SYMBOL voltage -1216 -256 R0
SYMATTR InstName V2
SYMATTR Value PULSE(-25 25 0 0 0 0 0.00005)
SYMATTR SpiceLine Rser=1
SYMBOL cap 320 -224 R0
SYMATTR InstName C3
SYMATTR Value 1n
SYMBOL Opamps/LT1497 1088 -32 R0
SYMATTR InstName U4
SYMBOL res 912 -80 R0
SYMATTR InstName R12
SYMATTR Value 680
SYMBOL res 816 32 R90
SYMATTR InstName R13
SYMATTR Value 680
SYMBOL cap 816 -64 R0
SYMATTR InstName C4
SYMATTR Value 100n
SYMBOL zener 560 192 R0
SYMATTR InstName D1
SYMATTR Value 1N750
SYMBOL zener 672 256 R180
SYMATTR InstName D2
SYMATTR Value 1N750
SYMBOL cap -16 -64 R0
SYMATTR InstName C5
SYMATTR Value 100n