Common Mode Rejection Ratio vs Common Mode Voltage

Question

I'm currently comparing characteristics of some different amplifiers, specifically their CMRR, and I came across this amplifier, which rather than listing an explicit CMRR, merely says:

Maximum Common Mode 1.2 V

As it is, I can't find a CMRR listed anywhere on the website, is this an equivalent statement for CMRR? If so, how would I calculate an equivalent CMRR from this seemingly uninformative statement? I've done a google search and a search on here for any information regarding expressing CMRR as a voltage, but so far no luck

Answer 1

That parameter says nothing about the CMRR. All it is telling you is the maximum common mode voltage (\$V_{comm}\$) the amplifier can handle while still meeting the other specifications.

^{simulate this circuit – Schematic created using CircuitLab}

$$ V_{comm} = \frac{V_+ + V_-}{2}$$

Provided that \$V_{comm} < 1.2V\$ (and really, they probably mean \$-1.2V < V_{comm} < 1.2V\$) then the amplifier will function according to specifications. Ostensibly, this common mode signal is attenuated, but if the CMRR is unspecified, then we don't know by how much.