Hello, could anyone tell me how the input and output behaves when the input to the op-amp is more than Vcm. For example, the op-amp that is in picture is LMV722 which has Vcm in the range 0 to 4.1V, what exactly happens when the input is more than 4.1V to LMV722 . I've read in forums that the op-amp will behave undesirably but I would like to understand what exactly happens in the case of LMV722 .

 

If one input exceed the range and the other is within, then modern opamps usually behave correctly - the output voltage is limiting at the expected supply rail.
If both exceed the range, then it is hard to say what will happen and the output could swing to the other supply rail, or oscillate, or anything else. Best course of action is to prevent this ever happening.

 

what exactly happens when the input is more than 4.1V to LMV722 . I've read in forums that the op-amp will behave undesirably but I would like to understand what exactly happens in the case of LMV722

The typical undesired behavior would be output inversion. The TI datasheet doesn't give a schematic of the opamp or mention how it would behave in that situation, so there's no way of knowing for certain.

The safest thing to do is to keep the inputs within the range specified by the datasheet.

 

Likely the only way to know is to test the actual device.
Otherwise use an op amp with a rail-rail CM input range.

 

Contact FAE at TI and ask that question, you will get precise
answer back from design department (typically). Also check
datasheet for max allowed input current to the pin when outside
CM Range, if not in there add that to the question list.

Regards, Dana.