| 摘要 |
A self-excited oscillation circuit comprises a turn-off transistor (Tr1) for turning off a transistor (Q1), a turn-off capacitor (C3) for outputting a voltage (Vb) to the base of the turn-off transistor (Tr1), and bias resistance (R1) for charging the turn-off capacitor (C3) by a voltage at a level corresponding to a drain current (Id) flowing when the transistor (Q1) is turned on. The self-excited oscillation circuit connects a resistor (R3) between the turn-off capacitor (C3) and a power supply section (50). This enables the turn-off capacitor (C3) to store an electric charge so that the voltage (Vb) is prevented from becoming lower than a predetermined bias voltage, which reduces the bias resistor (R1) and also the energy loss of the bias resistor (R1).
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