I've been experimenting some more with bandgap references, this time I'm attempting to design a Brokaw cell. I have the circuit below set up in LTSpice. I believe I've done the math correctly as the output seems to be in the right range for the bandgap of silicon, but the problem is I'm not getting the nice camel's hump tracking with temperature one would want! These Brokaw cells seem a lot more difficult to set up properly in simulation than some of the other bandgap designs. Any help would be appreciated, the LTSpice circuit follows:
Version 4 SHEET 1 1484 680 WIRE 144 -416 80 -416 WIRE 208 -416 144 -416 WIRE 384 -416 208 -416 WIRE 80 -368 80 -416 WIRE 208 -368 208 -416 WIRE 144 -320 -80 -320 WIRE 144 -224 144 -320 WIRE 208 -224 208 -272 WIRE 208 -224 144 -224 WIRE 384 -128 384 -416 WIRE 80 -80 80 -272 WIRE 320 -80 80 -80 WIRE 352 16 16 16 WIRE 80 64 80 -80 WIRE 208 64 208 -224 WIRE 16 112 16 16 WIRE 352 112 352 16 WIRE 352 112 272 112 WIRE 384 112 384 -32 WIRE 384 112 352 112 WIRE -224 160 -224 96 WIRE -224 160 -272 160 WIRE -208 160 -224 160 WIRE -144 160 -208 160 WIRE -80 160 -80 -320 WIRE 208 160 192 160 WIRE -272 208 -272 160 WIRE -144 208 -144 160 WIRE -32 256 -80 256 WIRE 80 256 80 160 WIRE 80 256 48 256 WIRE 96 256 80 256 WIRE 192 256 192 160 WIRE 192 256 176 256 WIRE 80 304 80 256 WIRE 80 416 80 384 FLAG 80 416 0 FLAG 288 -480 0 FLAG 288 -560 Vcc FLAG 144 -416 Vcc FLAG 384 192 0 FLAG -208 256 0 FLAG -224 16 Vcc SYMBOL res 64 288 R0 WINDOW 3 36 68 Left 0 SYMATTR Value 7850 SYMATTR InstName R1 SYMBOL res 192 240 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 28 56 VBottom 0 SYMATTR InstName R2 SYMATTR Value 470 SYMBOL voltage 288 -576 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL pnp 144 -272 R180 SYMATTR InstName Q3 SYMBOL pnp 144 -272 M180 SYMATTR InstName Q4 SYMBOL res 368 96 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL res 64 240 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 47k SYMBOL res -240 0 R0 SYMATTR InstName R5 SYMATTR Value 1MEG SYMBOL npn 16 64 R0 SYMATTR InstName Q1 SYMBOL npn 272 64 M0 SYMATTR InstName Q2 SYMATTR Value NPN 2 SYMBOL npn -272 160 R0 SYMATTR InstName Q6 SYMBOL npn -144 160 R0 SYMATTR InstName Q7 SYMBOL npn 320 -128 R0 SYMATTR InstName Q5 TEXT 496 -48 Left 0 !.dc temp -45 150