| 摘要 |
PURPOSE:To prevent carrier injection to a substrate when an input signal is reverse voltage even when the substrate is grounded by forming a pn-junction through an insulating film on an integrated circuit (IC) substrate to use it for an input protecting circuit to thereby isolate the substrate therefrom. CONSTITUTION:p-Type and n-type polycrystalline silicon layers 20, 21 are formed on an oxide thin film 19 of a p-type silicon substrate, and the layer 20 is connected through a wire 9 to the gate electrode 6 of a MOSFET7. Electrodes 12, 22 are grounded. The breakdown voltage of a diode 23 between the layer 20 and 21 is approx. 10 volts. When an input signal is now negative from the grounding potential, the diode 23 in conducted. Thus, electron is injected into layer 21 and absorbed to a terminal 22. Since the layer 21 is insulated from the substrate, electron is not injected into the substrate to thereby occur no erroneous operation in a dynamic circuit. When the input signal is positive high level, it is clamped at the breakdown voltage of the diode 23. Thus, higher than the breakdown voltage is not applied to the gate electrode 6 of the FET to thereby perform the protecting function thereof. |
