| 摘要 |
PURPOSE:To simplify the drive power supply and a driving circuit by connecting a gate of the 2nd n-channel FET and a gate of the 1st FET in a conventional example between a collector and an emitter of a bipolar transistor (Tr), obtaining a gate drive power supply from the connecting points and inserting the 2rd n-channel FET between the connecting point of the gate of the 2nd FET and the source of the said 2nd FET. CONSTITUTION:When a positive voltage drive signal is fed between the gate and emitter of th circuit of this invention, a bipolar Tr is turned on, FETs 1, 5 are turned on and the gate and source of the FET4 is short-circuit by the turning on of an FET5, which is turned off. The energy consumed by the turning-on of the FET4 is charged in the capacitor 8 via a diode 7 during this operating period. The charging voltage becomes a bias voltage of the FET4. On the other hand, when the voltage drive signal is zero, the Tr3 is turned off. The discharge energy of the capacitor 8 is an input capacitor energy between the gate and source of the FET4, and since the capacitance is very small in general, when the capacitance of the capacitor 8 is selected largely, a sufficient bias voltage is ensured.
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