sigma-delta ADC 运放的问题

四阶的sigam-delta modulator,第一级运放1/f噪声仿出来是-40db，好像太高. 差分输入尺寸已经很大了，280um^2，低功耗共8uA的电流。没看到讨论调制器运放噪声的资料，噪声方面有啥要求，望有经验者回答

噪声要求高的话，管子可以继续加大的
或者试试CDS 或者 choper stablization

补充一下，做低频带宽1K，考虑1/f噪声

switched-cap 的，就试试cds或者chop
continuous-time的,就用chop
去1/f很简单的

Your SDM must be used in audio type application. For such an applicaiton, 1/f is very critical, 280um^2 is not regarded big.However, what is your L and W, W/L=140u/2u and W/L=70u/4u will give you different results. Try to keep WL=const and optimized see if 1/f dominates at the first stage or its loading stage.Using chopper/CDS of course, is another solution, however, you must be careful. They will be some side-effected and constrained to use.

现在可以到-90db以下，再加choper应该就可以了吧

受教了,谢谢牛人