Version 4
SHEET 1 1892 680
WIRE 16 -448 -320 -448
WIRE 224 -448 16 -448
WIRE 16 -416 16 -448
WIRE 224 -416 224 -448
WIRE 16 -288 16 -352
WIRE 64 -288 16 -288
WIRE 112 -288 64 -288
WIRE 224 -288 224 -336
WIRE 288 -288 224 -288
WIRE 336 -288 288 -288
WIRE 16 -144 16 -288
WIRE 112 -144 16 -144
WIRE 16 -128 16 -144
WIRE 112 -128 112 -144
WIRE 224 -80 224 -288
WIRE -32 -32 -64 -32
WIRE 64 -32 64 -64
WIRE 64 -32 -32 -32
WIRE 160 -32 64 -32
WIRE 64 64 64 -32
WIRE 224 128 224 16
WIRE 336 128 224 128
WIRE 368 128 336 128
WIRE -320 144 -320 -448
WIRE 224 288 224 128
WIRE 320 288 224 288
WIRE 320 368 224 368
WIRE -320 448 -320 224
WIRE 64 448 64 144
WIRE 64 448 -320 448
WIRE 224 448 224 368
WIRE 224 448 64 448
WIRE -320 496 -320 448
FLAG -320 496 0
FLAG -320 -448 VS
FLAG 64 -288 Vzener
FLAG 288 -288 Vshunt
FLAG -32 -32 Vbase
FLAG 336 128 Vload
SYMBOL res 208 -432 R0
SYMATTR InstName R1
SYMATTR Value 120
SYMBOL voltage -320 128 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value PULSE(0 32 0 10 1 1 15)
SYMBOL res 48 48 R0
SYMATTR InstName R2
SYMATTR Value {Rbias}
SYMBOL res 304 272 R0
SYMATTR InstName R3
SYMATTR Value {Rload}
SYMBOL pnp 160 16 M180
SYMATTR InstName Q1
SYMATTR Value BC557B
SYMBOL pnp 112 -64 M270
SYMATTR InstName Q2
SYMATTR Value BC557B
SYMBOL References\\LT1004-1.2 16 -384 R0
SYMATTR InstName U1
TEXT -352 520 Left 2 !.tran 10
TEXT -1032 -24 Left 2 !.PARAM Rload 100\n#.STEP param Rload 1m 1000 200\n \n.PARAM Rbias 12k\n#.STEP param Rbias LIST 2k2 4k7 10k 15k 22k\n \n#.STEP TEMP -40 120 20\n.MEAS ILoad AVG I(R3)
TEXT -1032 -416 Left 2 ;Q2 compensates for the Tc of Q1\nso the current (10mA in this case) can be regulated\nwithin 10s of uA over the full temperature range.\n \nDimensioning:\nSet Rload very low (1 Ohm or so) and V+ as a slowly\nraising pulse from 3V to 20V. Measure the load current.\nAt reasonable values for R2 all curves will meet almost\nat one point. Measure I(R2) at this point and adjust R2\nfor this current at your final V+.\nAlso, compensation is optimal when Vzener = Vshunt.
TEXT -240 -424 Left 2 ;TLV431 is cheaper\nand does the same\n(but no LTSpice\nstandard model).
TEXT 352 -56 Left 2 ;Use dual Versions\n(BC857BS) for\nbetter thermal coupling.
TEXT -608 -520 Left 4 ;Improved Constant Current Source