Patent ID: 7445946

Claim:
A method of driving a light emitting device having a light emitting element and first and second driving transistors, the driving transistors being connected to the light emitting element, the driving transistors having a channel width W and a channel length L which satisfy L/W≧10, wherein the first and second driving transistors are connected in series between the light emitting element and a power source, wherein a channel width W 1 and channel length L 1 of the first driving transistor and a channel width W 2 and channel length L 2 of the second driving transistor satisfy (L 1 +L 2 )/W 1 ≧10 and (L 1 +L 2 )/W 2 ≧10, wherein a voltage is applied to a gate electrode of the first driving transistor and to a drain electrode or source electrode thereof so that a gate-source voltage V GS1 , source-drain voltage V DS1 , and threshold voltage V th1 of the first driving transistor satisfy 1 V≦|V DS1 |≦|V GS1 −V th1 | when the light emitting device emits light, and wherein a voltage is applied to a gate electrode of the second driving transistor and to a drain electrode or source electrode thereof so that a gate-source voltage V GS2 , source-drain voltage V DS2 , and threshold voltage V th2 of the second driving transistor satisfy 1 V≦|V DS2 |≦|V GS2 −V th2 | when the light emitting device emits light.