How to reduce noise figure of operational amplifier are studied in this paper.Through design of a low-noise OPA,introduc研究了如何从电路结构上减少运算放大器的噪声,以一种低噪声运放为例,着重介绍输入级设计,并借助计算机分析选择合适的输入器件尺寸,最后通过对运放噪声的仿真验证,得到了满意的结果。