Generation of residue voltage for pipeline ADC

[srujannnnn]

Hello,
I wanted to generate a residue voltage of Vref/12 using switched capacitor circuits.Transmission gate switches are being used.How do you determine the value of sampling capacitor,is there any reference available for that?.And also simulating this circuit using Cs=1.2pF didn't result in Vref/12.Is there any modification required in the circuit or the switches being used?
TIA

 

[24BSNR]

1) Missing phase on Cf to ground.
2) Please show simulation in/out gain, for empirical gain you received.

Cs size is usually set by SNR requirements of converter and hence kT/Cs. Higher Cs, better SNR. If you are just simulating for functionality, you can try something like 1pf.

For debugging, you can also start out with ideal switches first as transmission gates can add non-linear effects.