| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplitude modulation circuit which can automatically correct the characteristics in the absence of an analog voice signal. SOLUTION: An arithmetic circuit 2 adds an output setting bias voltage Vb to an input voice signal S1, and then outputs a bias voltage-added voice signal. When the absence of the voice signal S1 is detected by an absence-of-signal detection circuit 1, the arithmetic circuit 2 monitors the output Da of an A/D converter circuit 3 for converting the output of the arithmetic circuit 2 into a digital signal, to check whether or not a combination of power amplifiers which will be turned on in the absence of the sound signal S1 is the one which deteriorates the characteristics which is set by the bias voltage Vb. When the combination of power amplifiers is the one which deteriorates the characteristics, the bias voltage Vb is corrected. COPYRIGHT: (C)2008,JPO&INPIT
|
