A stimulator and a method of controlling the stimulator are provided. The method includes determining a waveform of a stimulus signal for a target, based on biological feedback of the target responding to a first stimulus signal, calculating a bioimpedance of the target based on a voltage waveform measured by applying the stimulus signal with the determined waveform to the target, and determining an operating voltage of the stimulator based on the determined waveform and the calculated bioimpedance.