Hi All

What is the exact meaning of the virtual ground of an op-amp, why we are calling as virtual ground. Is the point is directly connected or internally connected.

 

The answers to your question can be found here

http://www.allaboutcircuits.com/vol_3/chpt_8/5.html

Note in particular the virtual ground only applies to the inverting input of an amplifier, and that it is not directly connected to ground, either internally or externally.

 

It is not directly connected, but if you were to measure it with a meter it appears to be ground, hence the name. The op amp does an excellent job of making that point "appear" to be ground, even to instrumentation.