A signal sampled by a sampling transistor is amplified with low power consumption. A display voltage signal Vsig sampled by the sampling transistor is amplified by an amplifier circuit of this invention. A thin film transistor T1 which functions as a MOS capacitance is connected to a signal line DL to which the display voltage signal Vsig is outputted. A voltage boosting pulse VP1 is applied to a gate of the thin film transistor T1. And the thin film transistor T1 is switched from ON to OFF during change in the rising pulse. The amplifier circuit amplifies the signal through the use of difference between the gate capacitance of the thin film transistor T1 in ON state and the gate capacitance of the thin film transistor T1 in OFF state.