请教,本人用OPA2197搭了一个信号放大电路。如下图所示:不加任何输入信号时,按照上图的方式加直流偏置(PS:直流偏置2.5V由电压基准源REF3325提供),在只供电的情况下最后一级运放输出端有20mV左右的噪声。若将上图两处2.5V偏置都改为接地,则基本上无噪声输出。是否可以判断是2.5V基准源引入的噪声,被最后一级运放放大了101倍?若通过两级均分放大倍数的话,输出噪声还是存在,无法达到很干净。请问如何改进电路才能尽可能的减小输出噪声?
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