In one embodiment, the differential amplifier (DA) includes a first inverter inverting a first input signal and outputting the inverted first input signal to a current supply controller and a current drain controller. A second inverter inverts the first input signal and outputs the inverted first input signal as an output signal of the DA. The current supply controller supplies current to the first and second inverters in response to the inverted first input signal output from the first inverter during a first period. The current drain controller drains current from the first and second inverters in response to the inverted first input signal output from the first inverter during a second period. The output signal of the DA and the first input signal have differential phases with respect to each other and oscillate between logic high and low levels during the first period and the second period.