Abstract: This paper proposes a 12-bit, 40-Ms/s pipelined analog-to-digital converter (ADC) with an improved high-gain and wide-bandwidth operational amplifier (opamp). Based on the architecture of the proposed ADC, the non-ideal factors of opamps are first analyzed, which have the significant impact on the ADC's resolution. Then, the compensation techniques of the ADC's opamp are presented to restrain the negative effect introduced by the gain-boosting technique and switched-capacitor common-mode-feedback structure. After analysis and optimization, the ADC implemented in a 0.35 μm standard CMOS process shows a maximum signal-to-noise distortion ratio of 60.5 dB and a spurious-free dynamic range of 74.5 dB, respectively, at a 40 MHz sample clock with over 2 Vpp input range.

Key words: pipelined ADC