In addition to the core differential I/O voltage feedback gain block, there are two 6-kΩ resistors internally across the outputs to sense the average voltage at the outputs. These resistors feed the average voltage back into a V_CM error amplifier where the voltage is compared to either a default voltage divider across the supplies or an externally set VOCM target voltage. When the amplifier is disabled, the default midsupply bias string is disabled to save power.

To achieve the very-low noise at the low power provided by the THS4561, the input stage transistors are relatively large, thus resulting in a higher differential input capacitance (2.4 pF in Section 9.2). When using the 16-pin WQFN package and the internal feedback traces to the input side of the package, include the nominal trace impedance of 8.5 Ω in the design. These elements are not included in the TINA-TI™ model and must be added externally to a design intending to use the RGT package.