Patent ID: 8487844

Claim:
An EL display device comprising: a monitor circuit comprising: a monitor power supply line, a monitor transistor comprising a first terminal electrically connected to the monitor power supply line and a gate electrically connected to the monitor power supply line, a monitor light-emitting element comprising a first electrode electrically connected to a second terminal of the monitor transistor, a current source circuit electrically connected to a second electrode of the monitor light-emitting element, and an amplification circuit comprising an input terminal electrically connected to the second electrode of the monitor light-emitting element; and a pixel comprising: a light-emitting element comprising a first electrode electrically connected to an output terminal of the amplification circuit, and a driving transistor comprising a first terminal electrically connected to a second electrode of the light-emitting element, a second terminal electrically connected to a power supply line, and a gate electrically connected to a signal line, wherein each of the monitor transistor and the driving transistor comprises a semiconductor layer comprising an oxide semiconductor, and wherein a potential of the monitor power supply line is lower than a potential of the power supply line.