An electronic device has a photosensitive element, a charge storage element, and a node. The photosensitive element generates a current in response to illumination thereon. The charge storage element is coupled to the photosensitive element and is used to store charge in response to the current generated by the photosensitive element. The signal reading circuit is coupled to the photosensitive element, and the node is coupled between the photosensitive element and the charge storage element. The charge storage element and the photosensitive element are coupled in series, and the node is coupled to an end of the signal reading circuit.