| 摘要 |
PROBLEM TO BE SOLVED: To reduce noisy sound which may be produced at the time of the start or end of muting. SOLUTION: A muting circuit outputs AC output signals which are muted by fixing the amplitude level of AC input signals to the DC level. It has a DC offset eliminating section 221 which eliminates DC offset components in the AC input signals by passing them through an HPF (High Pass Filter) which is composed of a first operational amplifier, a muting signal generating section 224 which is composed of a second operational amplifier generating second DC offset at the same level as the first DC offset in the first operational amplifier and outputs muting signals indicating the second DC offset by fixing the input of the second operational amplifier to the DC level and a selector unit 226 which receives the AC input signals output from the DC offset eliminating section 221 and the muting signals output from the muting signal generating section 224 and selects the AC input signals and outputs them as AC output signals in a normal time or selects the muting signals and outputs them as AC output signals at the time of muting. COPYRIGHT: (C)2008,JPO&INPIT
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