PURPOSE: To decrease deterioration in an output signal waveform and to attain at a stable operation high speed by providing the 2nd switching means to a pulse transformer drive circuit and using a unipolar pulse signal from a signal generating circuit so as to apply drive control to the means.

CONSTITUTION: The pulse transformer drive circuit 3 is provided with a switching means TRIII 12 and a unipolar pulse signal outputted from a signal generating circuit 2 controls the means 12 so as to be driven when either of switching means TRI 10 and TRII 11 is not driven. Even when both the TRI 10 and TRII 11 stop driving and enter the linear operation, it is prevented that an input noise is amplified and outputted to a pulse transformer 4. That is, since any switching means is driven witnout fail at all times and all the switching means are not in the linear operating state at the same time, an excellent output waveform is obtained and the high speed and stable operation is attained.