A pixel circuit is disclosed. The pixel circuit includes a photodiode (PD), a transmission circuit, a reset circuit, a signal storage circuit and a buffer circuit. The transmission circuit is coupled between the PD and an ordinary floating diffusion (FD) node. The reset circuit is coupled to the ordinary FD node. The signal storage circuit is coupled to the ordinary FD node. The buffer circuit is coupled to the signal storage circuit. The signal storage circuit may store a PD signal on a specific node having a reduced leakage path in comparison with the ordinary FD node during a holding phase of the pixel circuit, wherein the holding phase is a time interval starting from a first time point at which the PD signal is stored on the specific node and ending at a second time point at which the pixel circuit is selected for performing a read-out operation.