Method for compensating frequency of wideband common mode feedback loop of two-stage operational amplifier

TLDR: In this paper, a method for compensating the frequency of a broadband common mode feedback ring circuit for a two-stage operational amplifier with Miller compensation was proposed, where the Miller compensation mechanism was used to reduce the area and power consumption of the common-mode feedback circuit.

Abstract: The invention discloses a method for compensating the frequency of a broadband common mode feedback ring circuit for a two-stage operational amplifier, belonging to the field of analog integrated circuit design A broadband feedback amplifier in the two-stage operational amplifier with the Miller compensation is used as the common mode feedback ring circuit so as to reduce the area and the power consumption of the common mode feedback circuit; the two-stage operational amplifier has only one main pole in the range of the unit gain bandwidth, a fully differential input and output structure is adopted, the sampling of the common mode output level is performed by the differential output end; and a control signal fed back by the common mode simultaneously controls the output level of a first-stage common mode and the output level of a second-stage common mode of the operational amplifier through a controllable bias circuit The frequency of the main pole of the broadband feedback amplifier is far higher than the unit gain bandwidth of the operational amplifier, therefore the margin of phase position of the common mode ring circuit is basically equal to that of the operational amplifier, thereby forming the stable feedback ring circuit The method has the advantages of few elements for a common mode feedback circuit, lower power consumption of the common mode feedback circuit and simpler and more convenient circuit design