PROBLEM TO BE SOLVED: To provide an amplifier capable of reducing the offset voltage.SOLUTION: An amplifier outputting a second signal by amplifying a first signal includes a comparator, a delay circuit, a first capacitive element, a second capacitive element, a first switch, and a second switch. The comparator generates a four signal by comparing the first signal with a third signal. A delay circuit generates a sixth signal by delaying a fifth signal, indicating the start timing of amplification operation, a certain delay time. The first capacitive element is connected between a voltage source and a first node supplying the third signal. The second capacitive element is connected between the first node and a second node supplying the second signal. The first switch is connected between the second node and a constant current source, and is controlled by fourth and fifth signals. The second switch is connected between the first node and second node, and is controlled by the fifth and sixth signals.SELECTED DRAWING: Figure 1