* SPICE netlist
D1 N001 0 1N4148 temp=18
D2 N002 0 1N4148 temp={t1}
R1 N009 N002 2.2k
R2 N003 N001 2.2k
R4 N008 Vout 1k
R6 Vh N005 1k
R7 Vh N004 6137
R8 N004 0 33k
C1 0 Vcc 100n
R10 Vh Vcc 3863
XU1 N003 N009 Vcc 0 Vout lm358 ;pnba In+)In-)V+)V-)OUT
V1 Vcc 0 10
R11 N007 N006 680
XU2 N008 N005 Vcc 0 N006 lm358 ;pnba In+)In-)V+)V-)OUT
D3 N007 0 L128-DRD1003500000
R3 N004 N003 1.2Meg
R5 N004 N003 1.2Meg
R9 Vout N009 1.2Meg
R14 Vout N009 1.2Meg
R15 N006 N008 390k
R16 N006 N008 100k
R12 N001 Vcc 12k
R13 N001 Vcc 68K
R17 N001 Vcc 120k
R18 N002 Vcc 12k
R19 N002 Vcc 68k
R20 N002 Vcc 120k
R21 N004 0 2700
R22 N003 N001 2.2k
R23 N009 N002 2.2k
.step param t1 28 18 0.05
.op

* LTspice schematic (.asc)
Version 4
SHEET 1 1312 784
WIRE -432 -312 -592 -312
WIRE 96 -312 -432 -312
WIRE 176 -312 96 -312
WIRE 256 -312 176 -312
WIRE 96 -280 96 -312
WIRE -592 -232 -592 -312
WIRE -592 -232 -656 -232
WIRE -528 -232 -592 -232
WIRE -432 -232 -432 -312
WIRE -336 -232 -432 -232
WIRE -240 -232 -336 -232
WIRE 96 -184 96 -200
WIRE 176 -184 96 -184
WIRE 96 -168 96 -184
WIRE 256 -168 256 -312
WIRE -592 -152 -656 -152
WIRE -528 -152 -592 -152
WIRE -336 -152 -432 -152
WIRE -240 -152 -336 -152
WIRE -80 -72 -80 -104
WIRE -80 -72 -176 -72
WIRE 0 -72 0 -104
WIRE 48 -72 0 -72
WIRE 96 -72 96 -88
WIRE 96 -72 48 -72
WIRE 96 -56 96 -72
WIRE -320 -40 -368 -40
WIRE -176 -40 -176 -72
WIRE -176 -40 -240 -40
WIRE -80 -8 -80 -72
WIRE 0 -8 0 -72
WIRE 176 8 176 -184
WIRE 240 8 176 8
WIRE 352 8 320 8
WIRE -592 56 -592 -152
WIRE -368 56 -368 -40
WIRE -368 56 -592 56
WIRE -320 56 -368 56
WIRE -176 56 -176 -40
WIRE -176 56 -240 56
WIRE 352 56 352 8
WIRE 368 56 352 56
WIRE 512 72 432 72
WIRE 656 72 592 72
WIRE 368 88 288 88
WIRE -176 104 -176 56
WIRE -128 104 -176 104
WIRE 32 120 -64 120
WIRE 128 120 32 120
WIRE 288 120 288 88
WIRE 288 120 208 120
WIRE -128 136 -176 136
WIRE 656 168 656 72
WIRE -432 184 -432 -152
WIRE -368 184 -432 184
WIRE -320 184 -368 184
WIRE -176 184 -176 136
WIRE -176 184 -240 184
WIRE -592 264 -592 56
WIRE -432 264 -432 184
WIRE 288 264 288 120
WIRE 384 264 384 232
WIRE 384 264 288 264
WIRE 464 264 464 232
WIRE 512 264 512 72
WIRE 512 264 464 264
WIRE 656 280 656 232
WIRE -368 296 -368 184
WIRE -320 296 -368 296
WIRE -176 296 -176 184
WIRE -176 296 -240 296
WIRE -96 296 -96 248
WIRE -96 296 -176 296
WIRE -16 296 -16 248
WIRE 32 296 32 120
WIRE 32 296 -16 296
WIRE -96 328 -96 296
WIRE -16 328 -16 296
WIRE 384 328 384 264
WIRE 464 328 464 264
WIRE -592 392 -592 328
WIRE -432 392 -432 328
FLAG 96 24 0
FLAG -96 88 0
FLAG 256 -104 0
FLAG 176 -312 Vcc
FLAG -96 152 Vcc
FLAG -592 392 0
FLAG -432 392 0
FLAG 96 -392 0
FLAG 400 40 Vcc
FLAG 400 104 0
FLAG 656 280 0
FLAG 48 8 0
FLAG 32 120 Vout
FLAG 176 -184 Vh
SYMBOL diode -608 264 R0
SYMATTR Value2 temp=18
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode -448 264 R0
SYMATTR Value2 temp={t1}
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL res -224 168 R90
SYMATTR InstName R1
SYMATTR Value 2.2k
SYMBOL res -224 40 R90
SYMATTR InstName R2
SYMATTR Value 2.2k
SYMBOL res 224 104 R90
SYMATTR InstName R4
SYMATTR Value 1k
SYMBOL res 224 24 R270
SYMATTR InstName R6
SYMATTR Value 1k
SYMBOL res 80 -184 R0
SYMATTR InstName R7
SYMATTR Value 6137
SYMBOL res 80 -72 R0
SYMATTR InstName R8
SYMATTR Value 33k
SYMBOL cap 272 -104 R180
SYMATTR InstName C1
SYMATTR Value 100n
SYMBOL res 112 -184 R180
SYMATTR InstName R10
SYMATTR Value 3863
SYMBOL OpAmps\\opamp2 -96 184 M180
SYMATTR InstName U1
SYMATTR Value lm358
SYMBOL voltage 96 -296 R180
SYMATTR InstName V1
SYMATTR Value 10
SYMBOL res 608 56 R90
SYMATTR InstName R11
SYMATTR Value 680
SYMBOL OpAmps\\opamp2 400 8 R0
SYMATTR InstName U2
SYMATTR Value lm358
SYMBOL LED 640 168 R0
SYMATTR InstName D3
SYMATTR Value L128-DRD1003500000
SYMBOL res 16 -120 R90
SYMATTR InstName R3
SYMATTR Value 1.2Meg
SYMBOL res 16 -24 R90
SYMATTR InstName R5
SYMATTR Value 1.2Meg
SYMBOL res 0 232 R90
SYMATTR InstName R9
SYMATTR Value 1.2Meg
SYMBOL res 0 312 R90
SYMATTR InstName R14
SYMATTR Value 1.2Meg
SYMBOL res 480 216 R90
SYMATTR InstName R15
SYMATTR Value 390k
SYMBOL res 480 312 R90
SYMATTR InstName R16
SYMATTR Value 100k
SYMBOL res -640 -136 R180
SYMATTR InstName R12
SYMATTR Value 12k
SYMBOL res -576 -136 R180
SYMATTR InstName R13
SYMATTR Value 68K
SYMBOL res -512 -136 R180
SYMATTR InstName R17
SYMATTR Value 120k
SYMBOL res -416 -136 R180
SYMATTR InstName R18
SYMATTR Value 12k
SYMBOL res -320 -136 R180
SYMATTR InstName R19
SYMATTR Value 68k
SYMBOL res -224 -136 R180
SYMATTR InstName R20
SYMATTR Value 120k
SYMBOL res 32 -88 R0
SYMATTR InstName R21
SYMATTR Value 2700
SYMBOL res -224 -56 R90
SYMATTR InstName R22
SYMATTR Value 2.2k
SYMBOL res -224 280 R90
SYMATTR InstName R23
SYMATTR Value 2.2k