Photodetector circuit, imaging device and method for driving a photo detector circuit

Photodetector circuit comprising: a photoelectric conversion element; a first transistor; a second transistor; a third transistor; and a fourth transistor, wherein a gate of the third transistor is connected via the first transistor is electrically connected to a first terminal of the photoelectric conversion element, wherein a gate of the fourth transistor is connected through the second transistor is electrically connected to the first terminal of the photoelectric conversion element, wherein the first transistor is configured to hold a gate potential of the third transistor according to an amount of light incident into the photoelectric conversion element when light is emitted from a light source, and wherein the second transistor is configured to a gate potential of the fourth transistor according to an amount of light to keep that is incident on the photoelectric conversion element when no light is emitted from the light source.