A power source for EL driving is built in an active matrix type EL display device, and the number of power sources externally attached is reduced. Therefore, the power source for EL driving is constructed by a transistor formed on a substrate, and its output circuit is constructed by a p-channel transistor of a source ground when the anode of an OLED is operated. Thus, the electric potential difference between a power voltage and an output voltage is reduced, and a power source circuit of small electric power consumption is constructed.