Using positive voltage reference on a negative supply

Question

Got a 9V,0,-9V power supply and want to get two stabilised voltage references at 2.5V and -2.5V.

Is it possible to use a +2.5V reference chip "upside down" to supply the -2.5V?

Answer 1

You could invert a +2.5 volt reference to -2.5 volts using an op-amp but I'd simply use a +2.5 volt shunt reference device like this one: -

And re-position is in the "negative circuit" like this: -

There are eighty-four +2.5 volt shunt references listed here on Mouser so I expect you'll be able to find one that is suitable in terms of accuracy and drift.

Note that the DS for the LM336 states on page 1: -

Further, since the LM136- 2.5 operates as a shunt regulator, it can be used as either a positive or negative voltage reference.

This applies to any shunt voltage reference of course.