The linear input voltage range of the INA12x input circuitry ranges from approximately 2 V less than the positive supply voltage to 2 V greater than the negative supply. A differential input voltage causes the output voltage to increase; however, the linear input range is limited by the output voltage swing of amplifiers A₁ and A₂. Thus, the linear common-mode input range is related to the output voltage of the complete amplifier. This behavior also depends on the supply voltage (see Figure 7-6).

Input overload can produce an output voltage that appears normal. For example, if an input-overload condition drives both input amplifiers to their positive output swing limit, the difference voltage measured by the output amplifier is near zero. The output of A₃ is near 0 V even though both inputs are overloaded.