AUTOMATIC GAIN CONTROLLER

摘要

PURPOSE:To design the titled controller in such a manner that it hardly follows the noise at a no-sound period but follows a sound signal quickly in the sound period by dividing the amplitude of an input signal by a maximum value of the amplitude to obtain an amplitude ratio and controlling the time constant in a way that the leading time constant is longer as the amplitude ratio is larger and smaller as it gets smaller. CONSTITUTION:An input signal 21 inputted to an input terminal 11 is smoothed and rectified by an amplitude calculation section 12 and becomes an amplitude signal 22. The signal 22 is inputted to a division section 13 and a maximum value hold section 14. The division section 13 divides the signal 22 by a maximum value signal 24 from the hold section 24 to obtain an amplitude ratio signal 23, the result is outputted to the hold section 14. The trailing time constant of the hold section 14 is controlled longer by the signal 23 as the signal 23 is larger and to be short as the signal 23 gets smaller. Under the condition of time constant, the hold section 14 obtains a maximum signal 24 being a maximum value of the signal 22. A variable gain amplifier section 15 is controlled to have a gain 25 by using the signal 24 and an output signal 26 is outputted from an output terminal 16.