| 摘要 |
PURPOSE:To obtain a highly reliable head core driving circuit that ensures high transmission efficiency by using a center tap type coil for an output head core and adding a simple FET and its protecting circuit to the driving circuit. CONSTITUTION:The coils 24A and 24B are connected to an output head core 20 via a center tap P. A FET1 is connected to the tap of the coil 24A; while a serial circuit of a capacity 3 and a resistance 4 is connected to the tap of the coil 23B in parallel with a diode 2. Then a power supply voltage VCC is applied to the tap P. A parallel circuit of a transistor TR6 and a diode 5 that passes an ON signal is connected to the gate of the FET1 for waveform shaping. The ON-signal is sent to a carrier and an information signal is superposed on the ON-signal via an AND gate 7. Then a transmission signal is sent selectively via an FF8. In addition, the FET1 is protected by resistances 41 and 42 and a TR43 and the counter electromotive force of the coil 24B is absorbed by a capacity 9 set in parallel with the tap P. An IC card is put into a gap of the core 20 and an input coil is properly positioned. Thus signals are transmitted satisfactorily by both coils 18 and 22. |
