Importance

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Abstract

A 1-bit D/A converter with a zero detect soft mute function is provided in such a manner that a counter is operated by detecting that a multibit digital signal is all zero for a constant period of time, and a feedback resistor of an op-amp in the analog low-pass filter is decreased stepwise based on a discrete value of the counter so as to be finally short-circuited so that a D/A convert output is fixed at a reference potential. The feedback resistor is composed of a plurality of resistors of first and second groups and first to third analog switches. A first digital control variable resistor is constituted by connecting the resistors of the first group in series and connecting a first analog switch selectively turned on/off in accordance with an output signal other than an LSB of the counter to respective nodes. A second digital control variable resistor is constituted by connecting the resistors of the second group in parallel and connecting a second analog switch controlled by the LSB of the counter to one side resistor in series. The first and second digital control variable resistors are connected in series, and a third analog switch is connected to both ends so as to constitute a feedback resistor.

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First Claim