格雷书上有关PSSR的计算

等效前

等效后

你第二张图画错了
CMRR=∞时看成是共模信号，vgs=-vsg

两个输入端接在一起，都是-vdd，即把vdd 等效到输入端

输入输出短接！

Hi LZ:
I suppose you've made a misstake, both(a) and (b) in the above picture are equivalent, not (b) is the equivalent of (a) as you supposed.
As Gray said, there are two sources of PSRR+, one is from VDD connected with rtail and another is from VDD connected with ro7.
According to superposition priciple, we can calculate each one respectively, and then add them up, and the sum is the total PSRR+.
That's my opinion, welcome to recorrect...