| 摘要 |
PURPOSE: To provide an enabling circuit with heat shut-down ability by providing a satisfactorily defined and comparatively temperature-stable turn on threshold provided with hysterisis, without pulling out supply current when an input is off. CONSTITUTION: 3V clamps Q2 to Q4 are added to the input terminal of a threshold detector network. These clamps prevent the saturation of transistors Q5 and Q6, when a high voltage is applied to an ON/OFF input terminal, and additionally gives the heat turning-off characteristic of the enable circuit. When the temperature of the circuit 10 is raised, a clamping voltage at the input terminal of the threshold detector network drops, due to the negative temperature coefficient of the clamps Q2 to Q4. A resistor R5 and a transistor Q12 operate to supply both the ON/OFF voltage hysterisis and heat turning-off hysterisis.
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