Charges on Switched Capacitor Circuit

[nxing]

Hello
I have a basic question regarding switched-capacitor integrator circuit, look at the attached drawing (from Paul Gray's book, chapter 6). on the top phase (sample phase), I am wondering what's the charge at right plate of C1? I am thinking because it's connected to ground (or any DC voltage), there should be no Charge, if that is the case, why we say at integrating phase (low drawing), the charge will be dumped to capacitor C2?

Thanks,

 

[LvW]

Hi nxing,

the answer is simple: During the sample phase the feedback capacitor must be discharged to be prepared to the next period (with charge transfer).
However, this assumes that the charge from the last period has been transferred before to the next stage which acts as a sample-and-hold stage (sample phase of the second stage). OK?
LvW

That means, you never can treat a S/C integrator as a separat and isolated stage because, in reality, it always is operated in conjunction with some other circuitry.