| 摘要 |
A switching amplifier including a PWM circuit 14 , a driver 15 , a switching output circuit 16 and an LPF 17 is provided with a fluctuation detection circuit 12 for detecting fluctuations in the power supply voltage. The fluctuation detection circuit 12 includes detection resistors 122 and 123 connected in series between a positive power supply 19 and a negative power supply 20 . A fluctuating signal RPL occurring at a fluctuation detection terminal 121 is supplied to the inverted input terminal of a differential amplifier 131 of a non-inverted amplifier circuit 13 . The non-inverted amplifier circuit 13 inverts the fluctuating signal RPL, mixes the inverted fluctuating signal into the input signal e<SUB>S</SUB>, amplifies the mixed signal, and supplying the amplified signal to the PWM circuit 14.
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