Op Amp Rails Question

[turjohn]

I've got a board that brings in 15V from an external supply and then I am generating -15V on the board with a chip from Maxim but it doesn't seem to want to work consistently from board to board so I am looking at an alternate solution from Linear. They've got a voltage inverter using a charge pump that I've breadboarded and it seems to work fine, except it doesn't give you exactly the negative of the input voltage, when I feed it 15V I get about -14.3V out. My question is this: what effect will this have on my op amps, if the positive rail is at 15V and the negative rail is at -14.3V? I don't plan on my signals going rail to rail, but will unbalanced rails introduce some offset at the outputs of the op amps?

Thanks in advance...

 

[chuckey]

The effect will be that signals that are referenced to earth, will appear to the op amp as referenced to +.35 V, which is nothing. If the line differential was huge, say +15 and -6 then the common mode voltage of the input stage could be exceeded.
Frank

 

[crutschow]

As long as the signal at the inputs is within the common-mode range of the op amp then a difference in the plus and minus voltages will generally have negligible effect on its operation.