| 摘要 |
PURPOSE:To absorb surge energy to below the dielectric strength of an FET by connecting a Zener diode and a diode which has the opposite polarity from the Zener diode in series between the drain and gate. CONSTITUTION:The series circuit of the Zener diode ZD1 and the diode D1 which has the opposite polarity from the Zener diode is provided between the drain and gate of the N channel FET. A voltage applied to the gate G of the diode D1 connected in series between the gate and drain of the FET operates not to be drawn to the drain D and when the FET is off, namely, when a control transistor TR is off, the Zener diode ZD1 feeds the surge energy applied to the FET back to the gate of the FET, thereby reducing the voltage between the drain and gate below a constant value. Consequently, the FET consumes the surge voltage and the gate is turned on before a voltage higher than the dielectric strength is applied, thereby lowering the surge voltage. |
