一种低失调CMOS轨到轨运算放大器研究

A Rail-to-Rail I/O Operational Amplifier

基于CMOS工艺设计了一款轨到轨运算放大器,整体电路包括偏置电路、输入级、输出级以及ESD保护电路。电路中的输入级使用了一种全新的架构,通过一对耗尽型NMOS管作为输入管,实现轨到轨输入,同时在输入级采用了共源共栅结构,能够提供较高的共模输入范围和增益;在输出级,为了得到满摆幅输出而采用了AB类输出级;同时ESD保护电路采用传统的GGMOS电路,耐压大于2 kV。经过仿真后可知,电路的输入偏置电流为150 fA,在负载为100 kΩ的情况下,输出最高和最低电压可达距电源轨和地轨的20 mV范围内,当电源电压为5 V时能获得80 dB的CMRR和120 dB的增益,相位裕度约为50°,单位增益带宽约为1.5 MHz。

A rail to rail operational amplifier was designed based on CMOS technology.The whole circuit includes bias circuit,input stage,output stage and ESD protection circuit.A new architecture was used in the input stage of the circuit.Rail to rail input could be realized through a pair of depletion NMOS tubes as input tubes.At the same time,the common source common grid structure was adopted in the input stage,which could provide high common mode input range and gain.In the output stage,class AB output stage is used to obtain full swing output.At the same time,the ESD protection circuit adopts the traditional ggmos circuit,and the withstand voltage is greater than 2 kV.After simulation,it can be seen that the input bias current of the circuit is 150 fA.When the load is 100 kΩ,the maximum and minimum output voltage can reach the range of 20 mV from the power rail and ground rail.When the power voltage is 5 V,80 dB CMRR and 120 dB gain can be obtained,the phase margin is about 50°,and the unit gain bandwidth is about 1.5 MHz.