Hello friend! hope below can help u about common mode rejection ration:

- CMRR is used for measuring the tendency of the device that is to reject the input signals.
- These signals can be from both input leads.
- CMRR at a high level is important, as the signals of interest are represented by a small set of fluctuations of voltage.
- The voltage fluctuations are superimposed on, possibly a large voltage offset.
- Superimposition of the signals might also be done, when the information of relevance is contained in the voltage difference between the two signals.

Thanks!