Patent ID: 8659519

Claim:
A pixel circuit comprising: a light-emitting element; and a drive thin film transistor (TFT) that supplies to the light-emitting element a first current controlling a gray scale according to luminance-current characteristics of the light-emitting element, wherein the drive TFT includes a semiconductor layer constituted by a channel region, a source region and a drain region, a gate electrode located at a top side or a bottom side of the semiconductor layer, and a back gate electrode disposed in an opposite side of the semiconductor layer to the gate electrode, wherein the drive TFT operates in a writing period so that a voltage is written between the gate electrode and the source region of the drive TFT by a second current flowing in the drive TFT and in a driving period so that the first current is supplied to the light-emitting element according to the voltage between the gate electrode and the source region of the drive TFT, and wherein different voltage levels are applied to the back gate electrode in the writing period and in the driving period so that a threshold voltage of the drive TFT in the driving period is higher than in the writing period, and thereby the second current is larger than the first current.