Version 4
SHEET 1 1320 680
WIRE 224 32 160 32
WIRE 352 32 288 32
WIRE 160 128 160 32
WIRE 160 128 96 128
WIRE 208 128 160 128
WIRE 352 128 352 32
WIRE 352 128 304 128
WIRE 592 128 352 128
WIRE 848 128 592 128
WIRE 1072 128 848 128
WIRE 1232 128 1072 128
WIRE 592 160 592 128
WIRE 160 208 160 128
WIRE 416 208 160 208
WIRE 528 208 496 208
WIRE 848 256 848 128
WIRE 256 272 256 192
WIRE 288 272 256 272
WIRE 368 272 352 272
WIRE 368 352 368 272
WIRE 416 352 368 352
WIRE 464 352 416 352
WIRE 640 352 464 352
WIRE 688 352 640 352
WIRE 848 352 848 336
WIRE 848 352 768 352
WIRE 1232 352 1232 128
WIRE 96 368 96 128
WIRE 848 368 848 352
WIRE 1072 368 1072 128
WIRE 320 384 320 352
WIRE 416 384 416 352
WIRE 464 384 464 352
WIRE 368 400 368 352
WIRE 368 400 352 400
WIRE 256 416 256 272
WIRE 288 416 256 416
WIRE 368 432 352 432
WIRE 368 480 368 432
WIRE 416 480 416 448
WIRE 416 480 368 480
WIRE 464 480 464 448
WIRE 464 480 416 480
WIRE 528 480 528 208
WIRE 528 480 464 480
WIRE 592 480 592 240
WIRE 592 480 528 480
WIRE 320 496 320 448
WIRE 848 512 848 448
WIRE 592 528 592 480
WIRE 96 624 96 448
WIRE 592 624 592 592
WIRE 592 624 96 624
WIRE 848 624 848 592
WIRE 848 624 592 624
WIRE 1072 624 1072 432
WIRE 1072 624 848 624
WIRE 1232 624 1232 432
WIRE 1232 624 1072 624
WIRE 592 640 592 624
FLAG 592 640 0
FLAG 592 480 Uref
FLAG 1232 128 U2
FLAG 320 496 0
FLAG 96 128 U1
FLAG 320 352 U1
FLAG 640 352 Ufb
SYMBOL voltage 96 352 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 18V
SYMBOL npn 208 192 R270
WINDOW 0 71 17 VRight 2
WINDOW 3 99 15 VRight 2
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL diode 400 448 M180
WINDOW 0 24 64 Left 2
WINDOW 3 -40 -57 Left 2
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL diode 448 384 R0
WINDOW 3 9 119 Left 2
SYMATTR InstName D3
SYMATTR Value 1N4148
SYMBOL zener 576 592 M180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D6
SYMATTR Value BZX84C6V2L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res 576 144 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 832 240 R0
SYMATTR InstName R4a
SYMATTR Value {Rx}
SYMBOL res 832 352 R0
SYMATTR InstName R4b
SYMATTR Value {2000.1-Rx}
SYMBOL res 832 496 R0
SYMATTR InstName R5
SYMATTR Value 2.1k
SYMBOL res 1216 336 R0
SYMATTR InstName R7
SYMATTR Value 100
SYMBOL Opamps\\UniversalOpamp2 320 416 M0
SYMATTR InstName U1
SYMBOL Misc\\EuropeanResistor 512 192 R90
WINDOW 0 5 56 VBottom 2
WINDOW 3 27 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 784 336 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 4.7k
SYMBOL cap 1056 368 R0
WINDOW 39 24 84 Left 2
SYMATTR InstName C1
SYMATTR Value 1u
SYMATTR SpiceLine Rser=10m
SYMBOL cap 352 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 4.7n
SYMBOL diode 288 16 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D1
TEXT 96 -120 Left 2 !.tran 0 1 0 1m startup
TEXT 96 -152 Left 2 !.step param Rx 50 2000 400
TEXT 96 -88 Left 2 !.options plotwinsize=0
TEXT 856 224 Left 2 ;Potentiometer
TEXT 816 240 Left 2 ;A
TEXT 808 448 Left 2 ;B
TEXT 96 -184 Left 2 ;.param Rx=50
RECTANGLE Normal 1024 464 800 208 2
CIRCLE Normal 384 320 272 240 2
CIRCLE Normal 512 256 400 160 2
CIRCLE Normal 784 416 672 288 2