When the primary design goal is a linear amplifier with high CMRR, the input pins must stay within the input operating range (V_ICR). These input pins are referenced off of each supply as an input headroom requirement. Specified operation at 25°C is maintained to the negative supply voltage, and to within 1.3 V of the positive supply voltage. The common-mode input range specifications in the table data use CMRR to set the limit. The limits are selected to make sure CMRR does not degrade more than 3 dB less than the minimum CMRR value if the input voltage is within the specified range.

During linear operation, the voltage difference between the input pins is small (0 V) and the input common-mode voltage is analyzed at either input pin, as both pins are at the same potential. The voltage at V_IN+ is simple to evaluate. In noninverting configuration (see Figure 7-1), the input signal (V_IN) must not violate the V_ICR. In inverting configuration (see Figure 7-2), the reference voltage (V_REF), must be within the V_ICR.

The input voltage limits have fixed headroom to the power rails and track the power supply voltages. For a single 5-V supply, the linear 25°C minimum input voltage ranges from 0 V to 3.7 V, and 0 V to 1.4 V for a single 2.7‑V supply. The delta headroom from each power supply rail is the same in each case (0 V and 1.3 V).