SBOS710D October 2014 – February 2018 LMH5401
The LMH5401 can set the output common-mode voltage to within a typical value of ±30 mV. If greater accuracy is desired, a simple circuit can improve this accuracy by an order of magnitude. A precision, low-power operational amplifier is used to sense the error in the output common-mode of the LMH5401 and corrects the error by adjusting the voltage at the CM pin. In Figure 72, the precision of the op amp replaces the less accurate precision of the LMH5401 common-mode control circuit while still using the LMH5401 common-mode control circuit speed. The op amp in this circuit must have better than a 1-mV input-referred offset voltage and low noise. Otherwise the specifications are not very critical because the LMH5401 is responsible for the entire differential signal path.