In a wave-shaping circuit, a charging switching element in series with an inductor is switched, a capacitor is charged with a back electromotive force generated by the inductor, a discharging switching element in series with a discharge resistor is switched, and the charge in the capacitor is discharged. By controlling the timing at which the charging switching element and the discharging switching element are switched, the power supply voltage can be increased and it is possible to generate a charge voltage for which the slope of the envelope can be determined. As a result, an output voltage with a desired output voltage waveform can be obtained from the charge voltage. The wave-shaping circuit is a simple circuit that does not include a transformer is used to increase the voltage of a low-voltage power supply and to form an output voltage waveform from a DC waveform.