For proper operation, the input common-mode voltage to the input terminal of the amplifier must not exceed the common-mode input voltage range. However, some single-supply applications can require the input voltage to exceed the common-mode input voltage range. In such cases, to bring the common-mode input voltage within the specifications of the amplifier, the circuit configuration of Figure 9-4 is suggested.

Figure 9-4 Circuit With Improved Common-Mode Input Voltage

Equation 3 is used to calculate R_PU: