| 摘要 |
PURPOSE:To ensure the protection from the abnormal voltage by connecting the source electrode of the FET containing the thick gate insulator film which operates with the depletion mode and is cut off when the input voltage exceeds the fixed level. CONSTITUTION:Depletion-type FET element Q5 is connected via drain resistance R between input terminal A and inner gate G6 of FET element Q6 to be protected. In other words, the gate and the source of element Q5 are connected in common to be then connected to the gate of element Q6, and diode D connecting to the substrate of Q5 is inserted to the contact between resistance R and the drain. In such constitution, the gate insulator film of Q5 is set thicker than the gate insulator film of Q6, and the source potential of Q5 is cut off immediately when it increases abnormally. Thus, gate G6 is cut off from terminal A. |
