Opamp input voltage clipping help

[venomanzer]

I'm making a comparator circuit using opamps, sort of like a voltage detector for 5v to -5v
Vcc as 5v and Vdd as ground, making logic 1 = 5v and logic 0 = 0v
but when I connect the function generator, it turn out that the negative voltage clipped at -1V (input clipping)
this work out fine when I change Vdd to -Vcc, but it turn my logic 0 to -5v

any ideas as to how I can fix the clipping problem? Thanks.

 

[KerimF]

Do you have a schematic? Just to see how the function generator output is connected to your opamp.

 

[FvM]

Three possible solutions:
- use a comparator with separate logic ground connection, e.g. LM311
- use level shifting at the output, e.g. with a resistive voltage divider
- use level shifting voltage dividers at the comparator input