Continuous-time common-mode feedback detection circuits with enhanced detection accuracy

Continuous-time common-mode feedback (CMFB) detector circuits for a fully differential amplifier with improved common-mode voltage detection accuracy are proposed, designed and analyzed. Firstly, we analyzed the proposed N-type CMFB detector, showing that it has two turning points when the differential voltage increases and it achieves very small deviation from the detected common-mode voltage. By combining the N-type and the P-type components directly, the proposed complementary CMFB detector circuit has further improved detection accuracy, and the simulation results with 0.13µm IBM process show only 6mV variation for rail-to-rail differential input voltage. A fully differential high gain wide bandwidth amplifier with the proposed CMFB detector circuit is designed and the simulation results have verified the proposed CMFB detector circuits.