| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier circuit capable of detecting a short-circuit if the output current is minute to protect an amplifier with a simple circuit, and an electronic device using the same. SOLUTION: A connection point between an input terminal 2 and an amplifier 3 is connected to one input of a comparison circuit 11, and the connection point between an amplifier 6 of a final step and an output terminal 8 is connected to the other input of the comparison circuit 11, and an output of the comparison circuit 11 is connected to a signal cutoff circuit 5. The comparison circuit 11 compares the voltages of input two signals, and when an output voltage of the amplifier 6 is lower than the input voltage of an amplifier 3, a signal cutoff circuit 5 is switched from a conductive state to a cutoff state. For this reason, the amplifier 6 can be protected from the overcurrent due to a short-circuit of an output terminal 8 without deteriorating a damping factor or a transient characteristic. Further, even when the level of a signal is low and only a slight current flows, the short-circuit of the output terminal 8 is detected, thereby protecting the amplifier 6.
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