Abstract: A sensing device includes a pixel unit and an output unit. The pixel unit includes a sensing element, a transfer transistor, a reset transistor, and an output transistor. The transfer transistor is coupled between the sensing element and a floating diffusion node. The reset transistor is coupled between a first node and the floating diffusion node. The output transistor has a control terminal coupled to the floating diffusion node and an input terminal coupled to the first node. During a readout period, the reset transistor is controlled by a reset phase to reset a level of the floating diffusion node. The output unit generates a pixel output signal at the first node according to the level of the floating diffusion node and a reference signal. During the readout period, the reference signal is at a higher level, and after the reset phase, the reference signal is at a lower level.