(a) CLock Feed through:

i) A MOS switch couples the clock transitions to the sampling cap through its ($C_{gd}\,\,or\,\,C_{gs}$) overlap capacitance.

ii) The effect is caused by the capacitive coupling between the clock input of precharge device and the dynamic output node.

iii) The coupling cap causes output of node to rise above $V_{DD}$ on the low to high transitions of the clock, assuming that the pull down n/w is turned off.

iv) The danger of clock feed through is that it may cause the (normally reverse biased) junction diodes of the precharged transistor to become forward-biased. This causes electron injection into the substrate, eventually resulting in faulty operation. CMOS latch up might be the another result of this injection.

(b) Charge injection:

i) A switched circuit at the sampling phase with a MOSFET as a switch is shown in fig(a). When the switch is ON, there is an amount of charge accumulated in the conducting channel of the transistor.

ii) When the switch turns OFF, this charge is injected to the either direction and part of the charge ($\Delta Q$) is dumped into capacitance $C_S$.

iii) The charge $\Delta Q$ results in an error voltage of $\Delta Q/C_S$ on $C_S$.

iv) In a fast switching - OFF condition when the falling time of the control clock is very fast, the X'tor channel disappears quickly.