The output voltage of the INA851 is developed with respect to the voltage on the output common-mode pin, VOCM. The starting point for most designs is to assign an output common-mode voltage for the INA851. For ac-coupled signal paths, this voltage is often the default midsupply voltage, so as to retain the most available output swing around the voltage centered at V_OCM. For dc-coupled signal paths, set this voltage between a minimum of V_S+ – 2.5 V and maximum of V_S– + 2.5 V. For precision ADC applications, this voltage is typically the input common mode voltage of the ADC.

The voltage at the VOCM pin is internally buffered to bias the fully differential output amplifier, eliminating the need for an additional external V_OCM buffer. While the buffer input is high-ohmic, the VOCM pin also connects through internal 500-kΩ resistors to V_CLAMP+ and V_CLAMP–, which sets the output common-mode voltage to midsupply in the event that the pin is floating.

While the V_OCM buffer has high small-signal bandwidth, be aware that large-signal steps with fast edges at the VOCM pin cause delays in the output. For best tracking between the buffer input and output signals, use rise times of 200 ns or greater for large steps.