算switched-cap的输出电容

SC

自顶一下，大家帮帮忙

我尝试回答下吧，不知道对不对。
设运放输出端接Vt激励，电流为it，运放增益为Av，连接运放输出的电容为C1。
则运放负相输入端的电压为Vt/Av。
所以(Vt-Vt/Av)*s*C1=it
再根据Zout=vt/it，得输出电容=(1+1/Av)*C1

誰能解答一下?

算得不对！

Assuming gain approaches infinity.
By the property of virtual short, one of the terminal of 1 pF capacitor in figure 1 is tied to AC ground.
So the equivalent capacitive load is ~1 pF for figure 1.
Likewise, the equivalent capacitive load is ~10 pF for figure 2.