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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 constant-cross-conduction constant-gain rail-to-rail operational amplifier is designed. The input stage adopts double current mirror controlled complementary differential pair structure to achieve rail-to-rail and constant transconductance. By analyzing the variation of op-amp voltage gain with common mode voltage , A feedforward constant gain control module is proposed, which can turn on or off the additional current source according to the common-mode voltage to keep the op-amp voltage gain constant.The output stage adopts feedforward type AB output structure to reach the rail The results of simulation and test show that the DC-DC gain of this operational amplifier is 125dB, and the unity gain bandwidth is 8.879MHz. The maximum change rate of voltage gain over the entire common-mode range is 1.69%.