Version 4
SHEET 1 1024 680
WIRE 96 -160 -16 -160
WIRE 240 -160 96 -160
WIRE 624 -160 240 -160
WIRE 768 -160 624 -160
WIRE 240 -128 240 -160
WIRE 768 -128 768 -160
WIRE 96 -112 96 -160
WIRE 624 -112 624 -160
WIRE 768 0 768 -48
WIRE 768 0 560 0
WIRE 240 32 240 -48
WIRE 768 32 768 0
WIRE -16 64 -16 -160
WIRE 96 80 96 -48
WIRE 176 80 96 80
WIRE 624 80 624 -48
WIRE 704 80 624 80
WIRE 560 144 560 0
WIRE 624 176 624 80
WIRE 656 176 624 176
WIRE 768 176 768 128
WIRE 768 176 736 176
WIRE 96 224 96 80
WIRE 128 224 96 224
WIRE 240 224 240 128
WIRE 240 224 208 224
WIRE 96 272 96 224
WIRE 624 272 624 176
WIRE 240 320 240 224
WIRE 240 320 160 320
WIRE 768 320 768 176
WIRE 768 320 688 320
WIRE 560 384 560 224
WIRE 624 384 624 368
WIRE 624 384 560 384
WIRE 96 432 96 368
WIRE 384 432 96 432
WIRE 624 432 624 384
WIRE 928 432 624 432
WIRE 96 496 96 432
WIRE 624 496 624 432
WIRE 240 512 240 320
WIRE 768 512 768 320
WIRE -16 592 -16 144
WIRE 96 592 96 576
WIRE 96 592 -16 592
WIRE 240 592 240 576
WIRE 240 592 96 592
WIRE 624 592 624 576
WIRE 768 592 768 576
WIRE 768 592 624 592
WIRE -16 624 -16 592
WIRE 624 624 624 592
FLAG -16 624 0
FLAG 624 624 0
SYMBOL res 224 -144 R0
SYMATTR InstName R2
SYMATTR Value 150K
SYMBOL LED 80 -112 R0
SYMATTR InstName D1
SYMATTR Value NSPW500BS
SYMBOL pnp 176 128 M180
SYMATTR InstName Q1
SYMATTR Value BC557C
SYMBOL voltage -16 48 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 15
SYMBOL npn 160 272 M0
SYMATTR InstName Q3
SYMATTR Value BC547C
SYMBOL LED 224 512 R0
SYMATTR InstName D2
SYMATTR Value NSPW500BS
SYMBOL res 80 480 R0
SYMATTR InstName R5
SYMATTR Value 150K
SYMBOL res 752 -144 R0
SYMATTR InstName R1
SYMATTR Value 150K
SYMBOL LED 608 -112 R0
SYMATTR InstName D3
SYMATTR Value NSPW500BS
SYMBOL pnp 704 128 M180
SYMATTR InstName Q2
SYMATTR Value BC557C
SYMBOL npn 688 272 M0
WINDOW 3 -53 -26 Left 2
SYMATTR Value BC547C
SYMATTR InstName Q4
SYMBOL LED 752 512 R0
SYMATTR InstName D4
SYMATTR Value NSPW500BS
SYMBOL res 608 480 R0
SYMATTR InstName R3
SYMATTR Value 150K
SYMBOL res 576 128 M0
SYMATTR InstName R4
SYMATTR Value 51meg
SYMBOL res 112 240 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R6
SYMATTR Value 10meg
SYMBOL res 640 192 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R7
SYMATTR Value 10meg
TEXT -200 168 Left 2 !.dc V1 3.5 15 .1
TEXT 304 400 Left 2 ;Ref out
TEXT 848 376 Left 2 ;Ref out\ncompensated