| 摘要 |
PURPOSE:To protect the internal circuit by a method wherein the first and the second gate electrodes mutually insulated are laminated on the surface between the source and the drain while the source and the first electrode are respectively connected to the reference voltage directly and through a diode then the second electrode and the drain are connected to the input terminal through a resistor. CONSTITUTION:The diode 30 is provided between the gate electrode 13 on the oxide film 12 with thickness of 500Angstrom and the ground while the other gate electrode 15 is laminated on said electrode 13 through the intermediary of the oxide film 14 with thickness of 5,000Angstrom . The gate electrode 15 and the drain layer 8 are respectively connected to the input terminal 10 and the internal circuit 20 through the intermediary of the resistors 6a and 6b. Due to the ratio of the oxide film thickness, if the threshold level from the electrode 13 is 1V, the protective FET is turned on when the input into the terminal 10VIN=10V limiting the voltage by means of the resistor 6a. The P-N junction is broken down around the N<+> layer 8 when VIN=22 or more, however, the electrode 13 charged with electron as the inverse leak to the diode 30 maintains almost constant voltage enabling to flow remarkable current and the conductivity is augmented corresponding to the voltage of the electrode 13 boosted by the positive hole. |
