An image sensor includes a sensor pixel. The sensor pixel includes a first transistor coupled between a first power source and a first node, where the first transistor is turned on in response to a first control signal, a light-sensing element coupled between the first node and a second power source, where the light-sensing element generates photocharges in response to incident light, a storage capacitor coupled in parallel to the light-sensing element between the first node and the second power source, and an amplifier including a plurality of transistors coupled in series between the first power source and an output line, where the amplifier outputs a sensing signal corresponding to a voltage of the first node in response to a first driving signal.