By holding a voltage that depends on a video signal in a first capacitor, holding a voltage that depends on a threshold voltage of a transistor in a second capacitor, and then applying a total voltage of the voltage held in the first capacitor and the voltage held in the second capacitor between a source and a gate of the transistor, even when the threshold voltage varies, a current corresponding to the video signal can be supplied to a load. The voltage that depends on the video signal and the voltage that depends on the threshold voltage of the transistor are separately acquired.