Patent ID: 7221226

Claim:
An amplifier circuit including a variable gain amplifier having a function of adjustment of an amplification gain according to a gain control signal for amplifying an input signal with the gain thus adjusted, thereby outputting an output signal within a predetermined level, said amplifier circuit comprising: a window comparator which compares a level of said output signal (which will be referred to as “output signal level” hereafter) with an attack reference level, and outputs an attack signal based upon an attack reference comparison result signal thus obtained, and which compares said output signal level with a recovery reference level different from said attack reference level, and outputs a recovery signal based upon a recovery reference comparison result signal thus obtained; an attack timing signal generating unit for outputting an attack timing signal at first predetermined time intervals; a recovery timing signal generating unit for outputting a recovery timing signal at second time intervals which are longer than said first predetermined time interval; and an action determining circuit which generates a gain reduction signal for decrementing said amplification gain by a first predetermined gain each time said attack timing signal is generated during output of said attack signal, and generating a gain increase signal for incrementing said amplification gain by a second predetermined gain each time said recovery timing signal is generated during output of said recovery signal, wherein the amplification gain of said variable gain amplifier is reduced or increased based upon said gain reduction signal or said gain increase signal while maintaining said amplification gain in a case that neither said gain reduction signal nor said gain increase signal is output.