Sometimes i come across different notations in Op Amps. Sometimes they are fed by V and ground, sometimes +V and -V. I am confused. Does ground mean minus?
Look at here:
http://www.williamson-labs.com/images/opamp-block_h.gif
and here:
http://www.williamson-labs.com/images/op-vg-1.gif
Best Answer
Opamps need to see a voltage accross their power terminals within a certain range. Generally the other voltages need to be limited to this range, and may need to be a bit less than this range to work properly.
Otherwise, the opamp has no idea what you think "ground" is. That is just the net you decided to use as the 0 V reference for other nets. As long as the opamp sees the right relative potentials on its pins, it doesn't care, in fact can't know whether any of them are at, above, or below ground.