| 摘要 |
PURPOSE:To surely prevent destruction of an output transistor (TR) at grounding or short-circuit by connecting a switch to the 2nd TR and controlling the switching by a comparator comparing a potential at an output terminal and a power voltage. CONSTITUTION:When a potential at the output terminal 2 is lower than a setting voltage V9 of a voltage source 9 at grounding, a switch 10 is turned off by the operation of a comparator 8 to interrupt the collector current of a TR 5. Thus, the collector current of a TR 3 whose base is connected to the emitter of the TR 5 is interrupted. On the other hand, the circuit is operated similarly at short-circuit as grounding and let the setting voltage of the voltage source 12 be V12, then the maximum voltage VCE when a large current flows to the collector of a TR 4 is expressed as VCE=Vcc-V12, where Vcc is the power voltage. Thus, no large current flows to the TRs 3,4 and no destruction is caused to them.
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