Research On The Design Of CMOS Rail-to-Rail Operational Amplifier

In recent years, electronics with battery supply are widely used, which cries for adopting low voltage analog circuits to reduce power consumption, so low voltage, low power analog circuit design techniques are becoming research hotspot. On the basis of analyzing MOS transistor constant-gm input stage and class AB output stage of operational amplifier, the paper designs a low voltage, high-gain, constant-gm CMOS rail-to-rail operational amplifier; it also analyzes the main reason that produces the Curvature and the V_be linearization Curvature-Corrected method is used for optimum project, then a bandgap reference circuit, which has a low temperature coefficient and a high power supply rejection ratio, is designed to give a constant reference. Second-order curvature-corrected and startup circuit are used in the bandgap circuit. The whole circuit is realized in Huahong-NEC 0.25μm CMOS process parameters provided by foundry for BSIM transistor models and is simulated in detail by Cadence spectre for op amp and bandgap and the results are analyzed, then the circuit is also optimized and simulated on the basis of analyzing. It' s indicated that the op amp has rail-to-rail input and output, which has the quality of higher gain, common mode rejection ratio, power supply rejection ratio, slow rate and lower noise. The output reference voltage' s temperature coefficient is 7.6 ppm/°C and has better temperature property and higher power supply rejection ratio, which can meet the CMOS Rail-to-Rail op amp requirements.Finally, the paper made the analysis and research for the matching character in the CMOS integrated circuit. Mismatch factors between the voltage and current of the MOS transistor are deduced by analyzing the transistor equation in saturation and linear region, and the influence of MOS transistor matching is stated. Therefore some effective methods and rules for designing MOS are presented systemically. It could be used as indispensably theoretic foundation for CMOS Integrated Circuit Design.