一种高增益高精度三级运算放大器设计

A Three Stage Operational Amplifier Design with High Gain and Precision

针对CMOS运算放大器存在的低精度和低增益的问题,提出了一种基于双极工艺的高增益高精度运算放大器。采用三级放大结构实现高增益,采用电阻负载的差分输入级达到降低输入失调电压和等效输入噪声电压的目标,同时预置电阻修调结构以进一步降低输入失调电压。由于传统的嵌套式密勒补偿会导致较高的功耗,且严重限制带宽,采用双零极点对和密勒(Miller)补偿的方式进行频率补偿,同时实现高单位增益带宽。测试结果表明,提出的三级运算放大器实现了140 dB的低频增益,10μV量级的输入失调电压和8.7 MHz的单位增益带宽。

To deal with the low precision and low gain of CMOS operational amplifiers,a high precision and high gain operational amplifier based on bipolar technology was presented.Three amplifi⁃er stages were used to realize high gain.Differential input stage with resistive loads was used to obtain low input offset voltage and equivalent input noise voltage with presetting trimming resistors to further reduce offset voltage.Traditional nested miller compensation could lead to high power and limit band⁃width severely.Dual doublets and miller compensation were adopted to frequency compensated and get wide unity gain bandwidth.Test results show that 140 dB gain and 10μV input offset voltage and 8.7 MHz unity gain bandwidth are achieved with the proposed amplifier.