A Design Methodology of Operational Amplifier for Σ-Δ A/D Converter
Chen Yixu, Ruzhang Li, Lichun Shi · 2011
A design methodology of operational amplifier(op-amp) for Σ-Δ A/D converter was proposed.A two-stage fully differential folded-cascode structure was adopted for the circuit.By using dynamic frequency compensation technique,frequency compensation in two operational modes was accomplished.A new common-mode feedback(CMFB) structure was proposed to achieve higher stability of common-mode level.The circuit was implemented using 0.35 μm mixed-signal technology.Simulation results indicated that the op-amp had a DC voltage gain of 120.5 dB and an output swing of ±4.2 V at 5 V supply voltage.