delaying : -z^-1/(1-z^-1),inverting
ph1 charge C1, ph2 charge transfer to C2, gain C1/C2.
delay-free : 1(1-z^-1),non-inverting
ph2 reset C1, ph2 charge transfer, gain C1/C2.
Distinguish, see whether Vin will affect Vout in the single phase. No matter ph1 or ph2.