| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that an emitter-base junction brings about the fluctuation of critical voltage on which a forward bias begins to operate, so that operating voltage as a protection circuit becomes unstable, since the contact which supplies electric potential to a base is formed on the outside of an emitter, when light enters the base, electric potential fluctuation of the base easily occurs by electrons induced by this (so-called optical latch up occurs), in a conventional input-protection circuit. SOLUTION: A base contact layer which supplies electric potential to the base is formed as a p<SP>+</SP>type fourth diffusion layer 14 just beside and in contact with the emitter in addition outside the emitter 12. This allows the base electric potential to be certainly fixed, the electric potential fluctuation by the optical latch up to be prevented, and a stable protection operation to be attained. COPYRIGHT: (C)2005,JPO&NCIPI
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