| 摘要 |
PURPOSE:To prevent the breakdown of the base-emitter junction of a transistor by providing between an outer lead terminal and a power supply terminal a P-N junction inversely biassed in normal operation and making regular direction continuity of abnormal voltage. CONSTITUTION:An NPN transistor TrQ1 and a base resistor R1 are formed at electrically-separated semiconductor ranges 20 and 21 respectively, and a P-N junction D3 by making a third semiconductor range at a semiconductor range 22. The third range and the electrode wiring 3 of which one end is connected to the emitter of TrQ1 are interconnected. In normal operation, to junction D3 is inversely biassed since the range 22 is connected to the electrode wiring 30 to be connected to a power supply terminal. The other end 40 of the base resistor R1 of TrQ1 is connected to the black box. With abnormally high voltage applied to an external lead terminal 4, the junction D3 is reqularly biassed for continuity. Therefore, the base-emitter junction D1 of TrQ1 can be prevented from breakdown. |
