Circuit having source follower and semiconductor device having the circuit

摘要

When a potential of a power supply line varies according to a flowing current, the gate-source voltage Vgs of a transistor also varies, leading to variations in the constant current between each source follower. In order to solve this problem, a potential Vb of the gate terminal of a transistor as a constant current source is changed in the same manner as a power supply line Vss which is connected to the source terminal of the transistor. Therefore, variations in the constant current are suppressed and variations in the output of the source followers are thus suppressed. In addition, by connecting the circuit having source followers to the output side of a signal line driver circuit, it can be prevented that luminance unevenness of a striped pattern is recognized in a display portion of a semiconductor device.