具有共模反馈和浮栅输入级的CMOS满幅运算放大器设计

Design of Rail-to-rail CMOS Amplifier with CM-feedback and Floating-gate Input Stage

利用输入跨导恒定技术设计了一种新的满幅运算放大器。该放大器利用浮栅差分对和负反馈电路作为输入级,将共模电平钳位在某一确定值,以保持输入跨导恒定。结合中间级、输出级的设计形成一个输入和输出均达到满幅度要求的整体运放结构。选用0.35μmCMOS工艺,对输入级和rail-to-rail运算放大器进行仿真分析。测试结果显示,这种电路新结构有利于拓展共模输入范围,有效地抑制了输入级的跨导变化,当±1.5V电源供电情况下,共模变化范围为±2.5V时,跨导仅有0.7%的波动。

A novel rail-to-rail amplifier was designed by using the input transconductance constant technique.In order to clamp the common mode level to a certain value and to keep the input transconductance constant,the amplifier used a floating-gates differential pair and a negative feedback circuit as input stages.Combined with the design of the intermediate stage and the output stage,a new structure amplifier with input and output meeting the full amplitude requirement was realized.Using the 0.35μm CMOS process,the input stage and the rail-to-rail operational amplifier were simulated and analyzed.The results show that the new structure of this circuit is beneficial to expand the common mode input range and suppress the transconductance variation of the input stage effectively.When the common mode variation range is within-2.5Vto+2.5 V,and under±1.5Vpower supply,the transconductance only has 0.7%fluctuation.