B
[email protected]
- Jan 1, 1970
- 0
Version 4
SHEET 1 880 680
WIRE 192 16 -288 16
WIRE 368 16 192 16
WIRE 192 64 192 16
WIRE 368 144 368 16
WIRE 192 160 192 144
WIRE 336 160 192 160
WIRE 544 176 400 176
WIRE -288 192 -288 16
WIRE -128 192 -288 192
WIRE 336 192 64 192
WIRE -288 256 -288 192
WIRE 192 272 192 160
WIRE 256 272 192 272
WIRE 400 272 336 272
WIRE 544 272 544 176
WIRE 544 272 480 272
WIRE -128 288 -176 288
WIRE 192 384 192 272
WIRE 416 384 192 384
WIRE 544 384 544 272
WIRE 544 384 480 384
WIRE 192 448 192 384
WIRE -288 560 -288 336
WIRE -176 560 -176 288
WIRE -176 560 -288 560
WIRE 192 560 192 528
WIRE 192 560 -176 560
WIRE 368 560 368 208
WIRE 368 560 192 560
WIRE -288 592 -288 560
FLAG -288 592 0
SYMBOL References\\LT1021-5 -32 240 R0
SYMATTR InstName U1
SYMBOL Opamps\\LT1006A 368 112 R0
SYMATTR InstName U2
SYMBOL voltage -288 240 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL res 176 48 R0
SYMATTR InstName R1
SYMATTR Value 100k
SYMATTR SpiceLine tol=0,1
SYMBOL res 176 432 R0
SYMATTR InstName R2
SYMATTR Value 100k
SYMATTR SpiceLine tol=0.1
SYMBOL res 496 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R3
SYMATTR Value 124k
SYMATTR SpiceLine tol=0.1%
SYMBOL res 352 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 1k
SYMATTR SpiceLine tol=1
SYMBOL cap 480 368 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 0.1µ
Sorry about the typo in the LTSpice circuit diagram - not 10k
resistors, but 100k resistors (corrected above).
The biggest soucre of uncertainy on the output is the tolerance on the
voltage reference - the LM4040C50FTA
offers +/-0.5% on 5V, or +/- 25mV, which shows up as +/-56.25mV on the
output, equivalent to +/-45mV on the 10V to 14V range of the supply
voltage to be digitised. The LT1021-5 would be a factor of ten better,
but does cost about ten times as much (at around $10), and the
contribution from the tolerances on the. 0.1% resistors would swamp
that.
SHEET 1 880 680
WIRE 192 16 -288 16
WIRE 368 16 192 16
WIRE 192 64 192 16
WIRE 368 144 368 16
WIRE 192 160 192 144
WIRE 336 160 192 160
WIRE 544 176 400 176
WIRE -288 192 -288 16
WIRE -128 192 -288 192
WIRE 336 192 64 192
WIRE -288 256 -288 192
WIRE 192 272 192 160
WIRE 256 272 192 272
WIRE 400 272 336 272
WIRE 544 272 544 176
WIRE 544 272 480 272
WIRE -128 288 -176 288
WIRE 192 384 192 272
WIRE 416 384 192 384
WIRE 544 384 544 272
WIRE 544 384 480 384
WIRE 192 448 192 384
WIRE -288 560 -288 336
WIRE -176 560 -176 288
WIRE -176 560 -288 560
WIRE 192 560 192 528
WIRE 192 560 -176 560
WIRE 368 560 368 208
WIRE 368 560 192 560
WIRE -288 592 -288 560
FLAG -288 592 0
SYMBOL References\\LT1021-5 -32 240 R0
SYMATTR InstName U1
SYMBOL Opamps\\LT1006A 368 112 R0
SYMATTR InstName U2
SYMBOL voltage -288 240 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL res 176 48 R0
SYMATTR InstName R1
SYMATTR Value 100k
SYMATTR SpiceLine tol=0,1
SYMBOL res 176 432 R0
SYMATTR InstName R2
SYMATTR Value 100k
SYMATTR SpiceLine tol=0.1
SYMBOL res 496 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R3
SYMATTR Value 124k
SYMATTR SpiceLine tol=0.1%
SYMBOL res 352 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 1k
SYMATTR SpiceLine tol=1
SYMBOL cap 480 368 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 0.1µ
The LT1021-5 is a ridiculous over-kill for the application, but it is
in the LTSpice library while the cheaper LM4040C50FTA I mentioned
earlier isn't.
I've also left out the 100nF bypass capacitor that even the LT1006
single supply op amp should have.
Almost any other low off-set single supply op amp that could survive
the peak supply voltage would do as well as the (elderly) LT1006.
I've followed Jim Thompson in figuring that the OP wants to digitise
the supply voltage range from 10V (which would give 5V at the output
of the LT1006 in this circuit) to 14V (which would give 0V at the
output of the LT1006, if the LT1006 could pull right down to the 0V
rail, which it can't, since it can only pull 40uA down to about 50mV).
The 0.1% resistors are E96 values and available ex-stock from Farnell,
some of them as single parts (though for many you have to buy five at
once, typically for more than a buck apiece).
Sorry about the typo in the LTSpice circuit diagram - not 10k
resistors, but 100k resistors (corrected above).
The biggest soucre of uncertainy on the output is the tolerance on the
voltage reference - the LM4040C50FTA
offers +/-0.5% on 5V, or +/- 25mV, which shows up as +/-56.25mV on the
output, equivalent to +/-45mV on the 10V to 14V range of the supply
voltage to be digitised. The LT1021-5 would be a factor of ten better,
but does cost about ten times as much (at around $10), and the
contribution from the tolerances on the. 0.1% resistors would swamp
that.