| 摘要 |
PURPOSE:To reduce number of parts by connecting the emitter of a transistor to the middle point of the primary winding of a pulse transformer and preventing magnetic saturation by letting flow current of reverse direction and the same quantity in the primary winding by a select signal. CONSTITUTION:When a burst signal 11 drives the primary winding of a pulse transformer 40, voltage at the middle point P of the primary winding becomes common voltage of an output differential amplifier circuit 10. On the other hand, a select signal 14 becomes logical low voltage, and emitter voltage of a transistor TR 20 is made to become lower than voltage of the middle point P. When the signal 11 is terminated, one of output 12, 13 of the emitter output differential amplifier circuit 10 becomes logical high level and another becomes logical low level. At this time, the signal 14 becomes logical high voltage. It is determined to make emitter voltage of the TR 20 higher than logical high level of output 12, 13. Thus, the circuit 10 becomes off, and current is shunted from the TR 20 to the primary winding, and accordingly, magnetic saturation is not caused. |
