A fingerprint sensor includes four transistors and a photodetector. The first transistor connects a second node with a third node based on a voltage of a first node, where the first node corresponding to a first electrode of the photodetector. The second transistor connects the second node with a read-out line based on a scan signal. The third transistor supplies a reset voltage to the first node based on a first reset signal. The fourth transistor connects the first node with the second node based on a second reset signal.