| 摘要 |
PURPOSE:To provide an input protecting circuit which has a high static dielectric strength and shows a high input resistance only when a high voltage is applied by a method wherein the other conductivity type diffused layer and the one conductivity type diffused layer which are formed in a substrate are connected in series to compose an input resistance. CONSTITUTION:The one end of a low concentration P-type diffused layer 2 is connected to an input terminal 1 and the other end is connected to the one end of a low concentration N-type diffused layer 4 and the other end of the low concentration N-type diffused layer 4 is connected to the internal wiring 14. When a negative high voltage is applied to the input terminal 1, the resistance value of the P-type diffused layer is significantly elevated compared to the value when the negative high voltage is not applied due to the spread of the depletion layer 3 of the low concentration P-type diffused layer 2. When a positive high voltage is applied to the terminal 1, the resistance value of the low concentration N-type diffused layer 4 formed in a P-type well 6 is significantly elevated compared to the value when the high voltage is not applied. A high input resistance can be provided only when a high voltage such as a static voltage and a low resistance can be provided when a normal logic level voltage is applied. Therefore, an input protecting circuit, which has little influence upon switching speed and has a high static dielectric strength can be obtained. |
