Panasonic Automotive Systems Co., Ltd.

Susumu Yoneta

Makoto Takemoto

A microphone module includes: a microphone element outputting a microphone signal representing collected sound; an amplifier circuit outputting an amplified signal obtained by amplifying a difference between the microphone signal and a reference voltage; a high-pass filter outputting a high-band amplified signal obtained by filtering the amplified signal; a buffer circuit outputting an audio signal obtained by buffering the high-band amplified signal; a first low-pass filter outputting a low-pass bias voltage obtained by filtering the audio signal superimposed on a DC power supply, and a separation circuit outputting an internal bias voltage obtained by removing the influence of an external circuit from the low-pass bias voltage. The second low-pass filter outputs the reference voltage obtained by filtering the internal bias voltage. A circuit from the high-pass filter to the amplifier circuit is set such that an open loop gain is smaller than 0 dB.

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Kanagawa, Japan

Susumu Yoneta