Why the gain of first stage is greater than second one for two-stage op？

Why the gain of first stage is greater than second one for two-stage CMOS op amps?

Please explain it for me.
Thanks you in advance.

noise比較低

第二级可以用来提供较大的摆幅，不用cascode结构，所以增益比第一级低；
第一级增益大的话方便进行频率补偿，将主极点放在第一级的输出节点处；
有利于减小第二级的mismatch和noise

no such mandatory requirments. Although it could reduce noise and psrr, it will make frequency compensation complicated. Trade-off considerations should be performed based on a specified envirement.

学习了

同学习。

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