A two-stage low-power amplifier with switch-capacitor common-mode feedback circuits

A low-power amplifier is designed to improve the performances of ADCs. The two-stage construction is adopted to provide bigger gain and wider swing at a power supply lower than 3.3V. Besides, the differential architecture is adopted to double the output swing while suppressing common noises. Special common-mode feedback circuits are designed to stable the common-mode outputs of the first and second stages but not to degenerate the output swing. A private switch is designed for the common-mode feedback circuits to eliminate the charge injection effect on the common-mode signals. The measurement results show that the ADC using the proposed amplifier has a SNR which is 4dB better than the ADC without the proposed amplifier.