A comparison amplification unit compares a level of a signal in a positive line with that of a signal in a negative line and latches a comparison result. An input terminal of a first inverter is connected to the positive line and an output terminal thereof is connected to the negative line. An input terminal of a second inverter is connected to the negative line and an output terminal thereof is connected to the positive line. An activation switch selectively switches between a state where the activation switch outputs a power supply voltage to the other power supply terminals of the inverters that are connected in common, such that the comparison amplification unit is inactivated, and a state where the activation switch outputs the ground voltage such that the comparison amplification is activated. The comparator outputs a signal corresponding to at least one of the signal in the positive line and the signal in the negative line at a timing after the comparison amplification unit is activated.