A pipelined analog-to-digital converter with less power consumption is provided. In one embodiment, the pipelined analog-to-digital converter comprises a first stage, a second stage, and a third stage. The first stage receives a first stage input signal to derive a first stage output signal and a first residue. The second stage receives a second stage input signal to derive a second stage output signal and a second residue, wherein the second stage input signal corresponds to the first residue. The third stage receives a third stage input signal to derive a third stage output signal and a third residue, wherein the third stage input signal corresponds to the second residue. The first, second and third stages share an operational amplifier by utilizing at least three phases to control the operational amplifier.