A novel common-mode sensing circuit with large input swing for Op-AMP with common-mode feedback

A novel continuous common-mode (CM) voltage sensing circuit is presented for Op-amp with large input swing. It has two stages: the first stage reduces the input swing, and the second detects the CM voltage. The proposed circuit is analyzed in detail. Finally, the circuit is designed with mixed-signal 0.18 um CMOS process, and the simulation results show that: the fluctuation of the sensing CM voltage is less than 1.5 mv when the input swing is up to plusmn0.8 V, which guarantees the minimization of the offset of the common-mode voltage and improves the linearity of the Op-amp.