Question about Swiched capacitor amplifier!! Help me plz

[pz5921087]

Hi,
I am now working on designing APS, the column amplifer I am going to use is shown in the figure,
It seems like a switched capacitor amplifer, but why it do not have a switch between VSF and Cin, how it works to sample the input? The DC bias from output was blocked by the feedback capacitor, so how to give the DC bias voltage to the negative input of opamp?
BTW should I use PSS and PAC to simualte the AC response?

Thanks!

 

[learning_curve]

Yes, you can use PSS and PAC to simulate AC response.
The switch Top will turn on which resets the capacitor, now the amplifier is in unity gain feedback
and the negative input of amp will get biased to Vref. So, I think there is no need for another DC bias.