A High-Gain, Low-Power Fully Differential Amplifier with Common-Mode Feedback for High-Speed and High-Precision Analog-to-Digital Converters
Yi Zhang · 2024
This paper presents a high-gain, low-power fully differential amplifier with common-mode feedback (CMFB) specifically designed for high-speed, high-precision analog-to-digital converters (ADCs). Fully differential operational amplifiers (FD-OPAs) are critical in modern analogue signal processing and communication systems due to their enhanced noise immunity, superior linearity, and broad dynamic range. The proposed design integrates an input stage, output stage, feedforward stage, CMFB circuit, and a wide-swing biasing network, all contributing to optimized performance metrics. The folded cascade input stage provides high gain and a wide input common-mode range, while the common-source output stage ensures low output impedance and high driving capability. The feedforward stage improves high-frequency performance by introducing a zero to compensate for phase delay, and the CMFB circuit provides a stable common-mode output level. Simulated in a 180-nm CMOS process with a 1.8 V supply, the design achieves a gain-bandwidth product (GBW) of 111 MHz, a differential DC gain of 83 dB, and a phase margin exceeding 60° across process corners. Monte Carlo analysis confirms robust performance and low noise, validating its efficacy for high-speed, high-precision ADCs. A comparative analysis demonstrates significantly better performance than prior works, particularly regarding gain, power efficiency, and figure of merit (FOM).