Patent ID: 8288807

Claim:
A semiconductor device comprising: a first terminal; a second terminal; a photoelectric conversion element; a diode-connected first transistor; and a second transistor, wherein one of a source and a drain of the second transistor is electrically connected to the first terminal, wherein the other of the source and the drain of the second transistor is electrically connected to the second terminal, wherein a gate of the second transistor is electrically connected to one of a source and a drain of the diode-connected first transistor, wherein the one of the source and the drain of the diode-connected first transistor is electrically connected to the first terminal through the photoelectric conversion element, wherein the other of the source and the drain of the diode-connected first transistor is electrically connected to the second terminal, wherein the diode-connected first transistor and the second transistor comprise an oxide semiconductor, and wherein the diode-connected first transistor and the second transistor have different threshold voltages.