is this kind of CMFB sensing circuitry used often in practical analog design? what is the popular CMFB sensing circuitry architectures used in practice. Could anyone give me some schematics or links, many thanks
Most are using a compensated resistive divider, as the present cicrcuit, I see it e. g. in TI THS4120 datasheet. The impedance level however depends on the technology, it's probably very different for a BJT based amplifier.