[sdiy] voltage reference advice

[David G. Dixon]

> > Does anybody have any preferences for voltage references?
> 
> I'm a big fan of the LM317 in a TO-92 package.
> 
> Replace one of the resistors in the voltage divider that sets your voltage
> value, with a trimmer and you can calibrate it to exactly the voltage you
> want.

The '317 is a "regulator" rather than a "reference".  However, looking at
the temperature stability plot on page 7 of the datasheet, and applying the
same formula for tempco as found in the '431 datasheet, it looks like it
should give a very similar tempco, if not even a little better.  The
relative reference voltage deviation would appear to be about 4mV/1.25V over
the temperature range of 0 to 75C, which gives 43ppm/C, which is very close
to the 46ppm/C discussed in the '431 datasheet.

Hmm....