Input Common-Mode Voltage Range

[IanBerry]

I've been playing with this op-amp lately because I want to make a super high-frequency SSTC driver (Not much reason other than to see what would happen). The issue is that the op-amp has been doing some weird things. Lots of distortion of a square wave, sometimes making it almost sinusoidal. I started to get frustrated because I was nowhere near the maximum frequency of the op-amp. I looked at the datasheet again and again until I found a little part that said:
Input Common-Mode Voltage Range    VCM    MIN VEE - 0.2      MAX VCC - 2.25       V
I was connecting the inputs to rail voltages. Do those numbers mean that the input voltage has to be 2.25 volts below the supply voltage or above 0.2 volts below the ground? I'll link the datasheet below.

https://datasheets.maximintegrated.com/en/ds/MAX4012-MAX4020.pdf

[digsys]

Absolutely correct. Even with RRI (rail-rail-Inputs) and RRO (rail-rail-Output), you have to be careful. Sometimes they are rated with no load / ideal conditons.
It may only be a few 10s-100s uV, can it is a trap. Instrument op-amps can go way above / below Supply.

[Ian.M]

Do those numbers mean that the input voltage has to be 2.25 volts below the supply voltage or above 0.2 volts below the ground?

Both.  AND not OR. If either input goes below Vee-0.2V or above Vcc-2.25V bad things happen.   The lower limit is right down to the ground (or negative) rail, but the upper limit is a PITA as it means you've got to prevent the inputs going closer to the positive rail than that, and you should design for a little more margin, say Vcc-2.5V, for safety.

[Rerouter]

On the flip side, you can find op amps with common mode input ranges far outside there voltage supply, which make things like bidirectional current monitoring much easier, but they are harder to find.