| 摘要 |
PURPOSE:To simplify the driving power supply and the driving circuit by providing additionally the 3rd FET, a diode, a Zene diode and a capacitor to a conventional circuit comprising the combination of a bipolar transistor (Tr) and an FET. CONSTITUTION:When a positive voltage drive signal is fed between gate and emitter of the circuit of this invention, the bipolar Tr3 is turned on. The energy charged in a capacitor 10 is discharged through a resistor 6 and an n-channel FET5. The charging voltage becomes a bias voltage becomes a bias voltage of an FET4. Thus, the bias voltage is ensured sufficiently by selecting a sufficient capacitance to the capacitor 10 so as to ensure a sufficient bias voltage when the Tr3 is turned off and selecting properly a discharge resistor 6. On the other hand, when the voltage drive signal is zero, the Tr3 is turned off. The capacitor 10 is charged to a constant voltage decided by a Zener diode 9 via a resistor 8 and a diode 7 during this period.
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