Patent ID: 7777232

Claim:
A display device comprising: a constant current source for supplying a constant current; an amplifier; a monitoring portion including a first monitoring pixel and a second monitoring pixel, the first monitoring pixel including: a first light-emitting element; and a first transistor, one of a source and a drain of the first transistor being electrically connected to a first electrode of the first light-emitting element, and the other of the source and the drain of the first transistor being electrically connected to the constant current source and a noninverting input terminal of the amplifier; the second monitoring pixel including: a third light-emitting element; and a third transistor, one of a source and a drain of the third transistor being electrically connected to a first electrode of the third light-emitting element, the other of the source and the drain of the third transistor being electrically connected to the constant current source and the noninverting input terminal of the amplifier, and a gate of the third transistor being electrically connected to a gate of the first transistor; a pixel portion including a pixel; the pixel including: a second light-emitting element; and a second transistor, one of a source and a drain of the second transistor being electrically connected to a first electrode of the second light emitting element, and the other of the source and the drain of the second transistor being electrically connected to an inverting input terminal and an output terminal of the amplifier, wherein a second electrode of the first light-emitting element, a second electrode of the second light-emitting element, and a second electrode of the third light-emitting element are held at a constant electric potential, wherein each of the first light-emitting element, the second light-emitting element, and the third light-emitting element has a first layer and a second layer formed between the first electrode and the second electrode, wherein the first layer contains a composite material including an organic compound and an inorganic compound, and wherein the second layer contains a light-emitting substance.