| 摘要 |
PURPOSE:To prevent characteristic deterioration and destruction of a signal amplifier section caused by an abnormal electric current, by connecting in series diodes for blocking reverse current with current limiter elements. CONSTITUTION:Diodes D5 and D8 for blocking reverse current are connected in series with bipolar transistors Q2 and Q3 working as current limiter elements. If an output terminal OUT is short-circuited with the ground when a current booster section 10A is driven so as to obtain a plus voltage at the output terminal OUT, the electric current of a bipolar transistor Q1 increases and the voltage drop of a resistance R3 exceeds a prescribed value. As a result, the bipolar transistor Q2 is conducted and its base bias current is caused to be divided. Therefore, the bipolar transistor Q1 is limited in electric current and protected.
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