A semiconductor device in which a signal current can be written quickly in a current source circuit of a current input type. A signal current is written after performing a pre-charge operation, thus the writing is performed quickly. In the pre-charge operation, a current is supplied to a plurality of circuits. The current size is set according to the number of the circuits to be supplied the current, which means the steady state can be obtained quickly. Note that a current may be supplied to a circuit other than the one to be input a signal in the pre-charge operation.