1. Field of the Invention
The present invention relates to a drive circuit for a light emitting element, and a display device having the drive circuit.
2. Description of the Related Art
Alight emitting element such as an organic EL element (OLED) is used for image display. The light emitting element conducts the light emitting operation while controlling the amount of current flowing into the light emitting element. A drive circuit that conducts light emitting drive of the light emitting element includes a drive transistor. The drive transistor has a threshold voltage, and the threshold voltage is varied depending on the manufactured drive transistor. In particular, when the drive transistor is formed of a low-temperature polysilicon thin film transistor (TFT), a variation in the threshold voltage of the drive transistor occurs due to a crystal variation of polysilicon formed in a process of subjecting a semiconductor layer to laser annealing. As a result, a display quality of the light emitting element is degraded due to the threshold voltage of the drive transistor, and the variation in the threshold voltage. For that reason, there is a need to correct a voltage to be applied to a gate of the drive transistor when the light emitting element emits light according to the threshold voltage of the drive transistor from the viewpoint of suppressing the degradation of the display quality. For example, Japanese Patent No. 4391857 discloses a pixel circuit in an organic electroluminescent display device having a function of correcting the threshold voltage (threshold voltage) of the drive transistor.
USPTO Backgrounds
USPTO Backgrounds