Patent ID: 6903731

Claim:
A light emitting device comprising: a first source signal line driver circuit, a second source signal line driver circuit, a first gate signal line driver circuit, a second gate signal line driver circuit, and a pixel portion; wherein said pixel portion has a plurality of pixels; wherein each of said plurality of pixels includes a light emitting element, a TFT for current control for controlling light emission from said light emitting element, a first TFT for switching and a second TFT for switching for controlling driving of said TFT for current control; wherein driving of said first TFT for switching is controlled by said first source signal line driver circuit and said first gate signal line driver circuit; wherein driving of said second TFT for switching is controlled by said second source signal line driver circuit and said second gate signal line driver circuit; and wherein gray-scale display is performed by controlling a length of a time period during which said light emitting element emits light.