A buffer circuit includes an amplifier circuit amplifying a difference between an input signal and a reference signal, providing a branch current that varies with a duty cycle of the input signal, and outputting a preliminary output signal on the basis of the amplified difference. The buffer circuit also includes a charge pump circuit charging/discharging a control node in response to the branch current to provide a control signal. The buffer circuit also includes a driver circuit configured to control pull-up strength and pull-down strength for the preliminary output signal based on control signal to thereby correct the duty cycle of the preliminary output signal in relation to a target duty cycle.