| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power amplifier for audible signal which protects a speaker and an output transistor from destruction when high-pass components exceeding an audible band are included in an input signal at a high level. <P>SOLUTION: A high-pass filter part 51 and a low-pass filter part 52 have characteristics that cutoff frequencies are fixed, set to a setting value equal to or more than an upper limit (between 18 and 22 kHz) of the audible band and frequency characteristics cross over. The high-pass filter part 51 extracts the high-pass components among frequency components of the input signal (1), and the low-pass filter part 52 passes low-pass components. An output signal (2) of the high-pass filter part 51 is input in a level control part 53, becomes an output signal (4) whose gain is controlled so that the level of the high-pass components does not exceed a predetermined value here, added to (mixed with) an output signal (5) of the low-pass filter part 52 in an adder 54, and becomes an output signal (6) of a high-pass restriction part 26. <P>COPYRIGHT: (C)2009,JPO&INPIT |
