前馈型轨到轨恒跨导恒增益CMOS运算放大器  

Feedforward rail to rail constant-gm constant gain CMOS operational amplifiers

作　　者：张为[1] 彭彦豪[1] 齐步坤[1] 姜宇[1] 

机构地区：[1]天津大学电子信息工程学院,天津300072

出　　处：《华中科技大学学报（自然科学版）》2011年第1期19-23,共5页Journal of Huazhong University of Science and Technology(Natural Science Edition)

基　　金：天津市科技支撑计划重点资助项目(10ZCKFGX3600);天津大学自主创新基金资助项目

摘　　要：设计了一种恒跨导恒增益的轨到轨运算放大器.输入级采用一倍电流镜控制的互补差分对结构,实现轨到轨和恒跨导.通过分析运算放大器电压增益随共模电压变化的原因,提出了一种前馈型恒增益控制模块,可以根据共模电压开启或关闭附加电流源,使运算放大器电压增益保持恒定.输出级采用前馈型AB类输出结构,以达到轨到轨输出效果.采用Chartered公司0.35μm工艺进行流片,仿真及测试结果表明:该运算放大器的直流开环增益为125dB,单位增益带宽为8.879MHz,在整个共模范围内电压增益最大变化率为1.69%.A rail-to-rail operational amplifier（OPA） with constant transconductance（gm） and constant gain was introduced.The input stage was a complementary differential pair controlled by the unity current mirror to realize rail-to-rail common-mode input and constant gm.Based on the relationship between the voltage gain and the common mode level,a novel feedforward constant gain control block was presented,turning on or off an additional current source to maintain the voltage gain unchanged.The feedforward class-AB structure was adopted in the output stage of the OPA to ensure rail-to-rail output.Sample chips were taped out with Chartered 0.35 μm process.The simulation and test results indicate that the low-frequency gain and unity-gain bandwidth of the proposed OPA circuit were 125 dB and 8.879 MHz respectively,and the voltage gain changes only about 1.69% over the common-mode input range.

关 键 词：运算放大器 前馈控制 恒增益 恒跨导 轨到轨 

分 类 号：TN722.7[电子电信—电路与系统]