An efficient frequency compensation scheme for CMFB loop in fully differential amplifiers

This paper proposes an efficient frequency compensation scheme for common-mode feedback (CMFB) loop in fully differential amplifiers (FDAs). In the proposed scheme, a compensating capacitor, C_C, is inserted to introduce an additional zero that compensates the non-dominant pole caused by parasitic capacitors, without compromising the differential-mode performance. Using the proposed compensation scheme, the CMFB loop achieves enough phase margin. Simulation results show that the phase margin is improved from 37° to 58°, 64° with C_C = 75 fF, 150 fF, respectively, when the load capacitor is 3 pF, while the power consumption remains largely the same.