Version 4
SHEET 1 1780 680
WIRE 1168 -128 1168 -224
WIRE 1168 -128 1040 -128
WIRE 1248 -128 1248 -224
WIRE 1360 -128 1248 -128
WIRE 656 -32 560 -32
WIRE 848 -32 736 -32
WIRE 1040 -32 1040 -128
WIRE 1040 -32 848 -32
WIRE 1120 -32 1040 -32
WIRE 1168 -32 1120 -32
WIRE 1360 -16 1360 -128
WIRE 1360 -16 1232 -16
WIRE 1456 -16 1360 -16
WIRE 1584 -16 1536 -16
WIRE 1776 -16 1584 -16
WIRE 1168 0 1088 0
WIRE 1584 32 1584 -16
WIRE 560 48 560 -32
WIRE 1088 112 1088 0
WIRE 1584 128 1584 96
WIRE 64 208 64 192
WIRE 64 208 16 208
WIRE 16 224 16 208
WIRE 64 224 64 208
WIRE 656 240 576 240
WIRE 848 240 848 -32
WIRE 848 240 736 240
WIRE 576 256 576 240
WIRE 1584 256 1584 208
FLAG 16 224 0
FLAG 64 112 V+
FLAG 64 304 V-
FLAG 560 128 0
FLAG 576 336 0
FLAG 1120 -32 Vsum
FLAG 1088 112 0
FLAG 1200 -48 V+
FLAG 1200 16 V-
FLAG 1584 256 0
SYMBOL voltage 64 96 R0
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL voltage 64 208 R0
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL voltage 560 32 R0
SYMATTR InstName V3
SYMATTR Value 0
SYMBOL res 752 -48 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 100k
SYMBOL res 752 224 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 100k
SYMBOL voltage 576 240 R0
SYMATTR InstName V4
SYMATTR Value {vb}
SYMBOL Opamps\\AD795 1200 -80 R0
SYMATTR InstName U1
SYMBOL res 1264 -240 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 66k
SYMBOL res 1552 -32 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL diode 1568 32 R0
SYMATTR InstName D1
SYMBOL voltage 1584 112 R0
SYMATTR InstName V5
SYMATTR Value 2.7
TEXT 256 -328 Left 2 !;.param vb 0\n.step param vb list 0 -5
TEXT -4 378 Left 2 !.dc V3 0 -5 -.1