| 摘要 |
A speech detection circuit includes an amplifier for amplifying an input audio signal and having a variable gain, a rectifying circuit for rectifying an output signal of the amplifier, a comparator for comparing an output signal level of the rectifying circuit with a reference level, and a control circuit for outputting a control signal based on an output signal of the comparator. The control circuit outputs a control signal which indicates a power save mode after a predetermined time elapses from a time when the output signal level of the rectifying circuit becomes less than or equal to the reference level, and outputs a control signal which indicates a normal mode immediately when the output signal level of the rectifying circuit becomes greater than the reference level. The amplifier receives the control signal output from the control circuit and reduces its gain when the control signal indicates the power save mode. |
