| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier circuit that prevents a noise signal from being continuously amplified for output when amplifying an input signal while changing a gain so that the amplitude of an output signal approaches a prescribed reference value, and can perform control so that the amplitude of the output signal does not change unnaturally. SOLUTION: The amplifier circuit detects the amplitude of the output signal outputted by an amplifier having variable gain, changes the gain of the amplifier so that the amplitude of the output signal approaches the prescribed reference value based on the detected amplitude of the output signal, determines whether the input signal inputted to the amplifier is a signal to be amplified or a noise signal, and attenuates the output signal, while increasing an attenuation factor gradually when it is determined that the input signal is a noise signal. COPYRIGHT: (C)2009,JPO&INPIT
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