Version 4
SHEET 1 880 768
WIRE -288 -16 -336 -16
WIRE -240 -16 -288 -16
WIRE -112 -16 -144 -16
WIRE 256 -16 -112 -16
WIRE 352 -16 256 -16
WIRE -288 0 -288 -16
WIRE 256 0 256 -16
WIRE -288 96 -288 80
WIRE -192 96 -192 48
WIRE -192 96 -288 96
WIRE 32 96 -192 96
WIRE 256 96 256 80
WIRE 256 96 96 96
WIRE -192 192 -192 96
WIRE -64 192 -192 192
WIRE 256 192 256 96
WIRE 256 192 192 192
WIRE 256 224 256 192
WIRE -112 320 -112 -16
WIRE -64 320 -112 320
WIRE 256 320 256 304
WIRE 256 320 192 320
WIRE 256 384 256 320
WIRE 256 384 192 384
WIRE 352 384 256 384
FLAG 352 -16 OUT
IOPIN 352 -16 Out
FLAG -336 -16 IN
IOPIN -336 -16 Out
FLAG 352 384 GND
IOPIN 352 384 Out
SYMBOL npn -240 48 R270
WINDOW 0 122 28 VRight 0
WINDOW 3 91 -2 VRight 0
SYMATTR InstName Q1
SYMATTR Value 2N2219A
SYMBOL res -304 -16 R0
SYMATTR InstName R1
SYMATTR Value 680
SYMBOL res 240 -16 R0
SYMATTR InstName R2
SYMATTR Value {rser}
SYMBOL res 240 208 R0
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL cap 96 80 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 1nF
SYMBOL Opamps\\LT1431 64 288 R0
SYMATTR InstName U2
TEXT -328 448 Left 0 !.param Vref=12V rser=({Vref}-2.507843V)/250uV
RECTANGLE Normal 352 464 -336 -96