Light emitting device and electronic appliance

摘要

The present invention is to provide a light emitting device capable of obtaining a certain luminance without influence by the temperature change, and a driving method thereof. A current mirror circuit formed by using a transistor is provided for each pixel. The first transistor and the second transistor of the current mirror circuit are connected such that the drain currents thereof are maintained at proportional values regardless of the load resistance value. Thereby, a light emitting device capable of controlling the OLED driving current and the luminance of the OLED by controlling the drain current of the first transistor at a value corresponding to a video signal in a driving circuit, and supplying the drain current of the second transistor to the OLED, is provided.

主权项

1. A light emitting device comprising:
a signal line; a power source line; a light emitting element comprising a light emitting layer; a first transistor; a second transistor; a third transistor; a fourth transistor; a first insulating layer over a gate electrode of the second transistor; a conductive layer under a counter electrode of the light emitting element; and a second insulating layer interposed between the first insulating layer and the counter electrode of the light emitting element, wherein a gate electrode of the third transistor and a gate electrode of the fourth transistor are connected with each other, wherein one of a source and a drain of the third transistor and one of a source and a drain of the fourth transistor are connected with one of a source and a drain of the first transistor, wherein the other of a source and a drain of the third transistor is connected with the signal line, wherein the other of a source and a drain of the fourth transistor is connected with a gate electrode of the first transistor, wherein the other of a source and a drain of the first transistor is connected with the power source line, and wherein one of a source and a drain of the second transistor is directly connected with a pixel electrode of the light emitting element.