Version 4 SHEET 1 880 680 WIRE 432 -80 416 -80 WIRE 528 -80 512 -80 WIRE 416 -64 416 -80 WIRE 512 -64 512 -80 WIRE 224 -32 208 -32 WIRE 208 0 208 -32 WIRE 208 0 112 0 WIRE 304 0 208 0 WIRE 112 32 112 0 WIRE 304 32 304 0 WIRE 112 144 112 112 WIRE 208 144 112 144 WIRE 304 144 304 112 WIRE 304 144 208 144 WIRE 208 160 208 144 FLAG 416 16 0 FLAG 208 160 0 FLAG 512 16 0 FLAG 512 -80 VRb FLAG 208 -32 VCC FLAG 416 -80 VCC SYMBOL res 96 16 R0 SYMATTR InstName Rb SYMATTR Value R=rb*V(VRb) SYMBOL res 288 16 R0 SYMATTR InstName Rp SYMATTR Value R=rb*rc/(rb-rc) SYMBOL voltage 416 -80 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 1V SYMBOL voltage 512 -80 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 1V TEXT 328 240 Center 2 !.step param rb list 100k 150k 200k 500k TEXT 384 200 Left 2 !.param rc 50k TEXT 384 168 Left 2 !.dc V2 0 1 1m