| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier circuit that can simply be realized as an audio amplifier with an excellent electric characteristic while suppressing the cost. SOLUTION: A negative feedback path of an operational amplifier 10 has a 1st negative feedback path NF1 not through an electronic volume 11, a 2nd negative feedback path NF2 passing through the volume 11, and a negative feedback analog switch 12A that closes either of them, and an output path of the operational amplifier 10 has a 1st output path Op1 not through the electronic volume 11, a 2nd output path Op2 passing through the electronic volume 11, and an output use analog switch 12B that closes either of them. An external CPU 1 controls the electronic volume 11 and the analog switches 12A, 12B so as not to simultaneously close the 2nd negative feedback path NF2 and the 2nd output path Op2.
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