Patent ID: 8111215

Claim:
A display device comprising: a pixel portion comprising a first transistor and a light emitting element over a substrate; a source signal line driver circuit operationally connected to the pixel portion; and a circuit comprising: a second transistor; a current source configured to supply a current flowing through the second transistor; a buffer amplifier electrically connected to a node between the second transistor and the current source; a differential amplifier including a first input terminal and a second input terminal, wherein the node is electrically connected to the first input terminal through the buffer amplifier, and wherein the second input terminal is electrically connected to a power source; and an adder circuit configured to add a voltage output from the differential amplifier and a video signal, wherein the source signal line driver circuit is configured to receive an output video signal from the adder circuit, and wherein the light emitting element comprises a first electrode and second electrode and an electroluminescent layer between the first electrode and the second electrode.