| 摘要 |
PURPOSE:To constitute an effective protection circuit taking a rise in temperature of a transistor into account, by making use of the temperature dependency of the base- emitter voltage of the protective transistor. CONSTITUTION:Output-stage transistor Tr12 and protective Tr18 are fitted to the same radiation piece 31 with good thermal coupling. Therefore, Tr18 rise in temperature in accordance with the temperature rise of Tr12. On the other hand, since base-emitter voltage VBE of Tr18 has a temperature coefficient of approximate -2mV/ deg.C, a current value determining protection characteristics as the temperature rises, so that Tr18 will be easy to conduct. Adequate fixation of Tr18 to radiation piece 31 allows variation of a safe operation region due to the temperature rise to agree with that of protection characteristics, so that Tr12 can be prevented from breaking down even when the temperature rises. |
