An image sensor is provided. In one aspect, the image sensor includes a pixel coupled to an output line. The pixel includes a photodiode configured to generate electrical charges in response to light and a supply circuit configured to supply a voltage to the photodiode to keep a voltage of the photodiode at or above a threshold level in an integration time. In another aspect, the pixel includes a supply circuit configured to selectively supply voltage to the photodiode in a first charge holding capacity and a second charge holding capacity.