US Patent 7847593 Semiconductor device, display device, and electronic device

To provide a semiconductor device which operates stably with few malfunctions due to noise, with low power consumption, and little variation in characteristics; a display device including the semiconductor device; and an electronic device including the display device. An output terminal is connected to a power supply line, thereby reducing variation in electric potential of the output terminal. In addition, a gate electrode potential which turns ON a transistor is maintained due to the capacitance of the transistor. Further, change in characteristics of the transistor is reduced by a signal line for reverse bias.