| 摘要 |
PURPOSE:To protect an input stage of controlling a small signal even if an output stage malfunctions by providing input protecting means for blocking the arrival of the malfunction state of the output stage at the input stage. CONSTITUTION:In order to avoid the forward connections of parasitic diodes D1, D2 from an output stage to an input stage, an n<+> type emitter diffused layer 4 and a p<+> type base diffused layer 3 are set through a contact region OP5 to the same potential, and disposed adjacently without an n<-> type layer 2 therebetween. An input protecting diode D2 is inserted with a cathode at the region CP5 side between the region CP5 and an inverter G. A diode D3 has sufficiently larger reverse breakdown strength than a voltage VE. Accordingly, even if the malfunction of the output stage of a transistor Q occurs, the input stage of the inverter G is not affected by the influence of the malfunction, and a microcomputer externally attached to the terminal P1 neither breaks down nor malfunctions.
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