PURPOSE: To obtain both the narrow- and wide-duration pulses by only one unit of the gate transformer, by connecting the capacitor and the resistance in parallel to the limit resistance of the Royer's oscillator.

CONSTITUTION: The serial circuit of vibration preventing resistor 23 and capacitor 24 is connected in parallel to limit resistor 14 of the Royer's oscillator. Here the resistance value of resistor 23 is set lower than the resistance value of resistor 14 in order to obtain the necessary pulse value. As a result, the output voltage having waveform 3 is induced at the secondary side of gate transformer 21. This output voltage then receives the full-wave rectification, and thus gate signal having waveform 4 obtained by compounding the narrow- and wide-duration pulses can be obtained. In such way, both the narror- and wide-duration pulses can be obtained by only one unit of the gate transformer.