| 摘要 |
PROBLEM TO BE SOLVED: To provide an input protection circuit which induces a punch-through phenomenon earlier than an N-channel transistor so as to restrain a small leakage current from occurring when an outside surge voltage higher than a certain voltage is applied, by a method wherein the source of a P-channel transistor where a channel length is thinned is grounded, and a well and a gate are connected to the drain of the P-channel transistor. SOLUTION: A surge resistor 8 which weakens the waveform of an outside surge voltage, a protection diode 9 which shunts the surge voltage to a ground when a surge voltage higher than a certain voltage is applied, and an output N channel transistor 10 which protects an inner circuit against the surge voltage, are provided in an input protection circuit 12. Furthermore, the source of a P-channel transistor 11 (surge removing means) is connected to a ground, and a well and a gate are connected to the drain of the P-channel transistor 11. At this point, the channel length of the P-channel transistor 11 is thinned, by which the P-channel transistor 11 induces a punch-through phenomenon earlier than the N-channel transistor 10 when an outside surge voltage higher than a certain voltage is applied.
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