AUTOMATIC GAIN CONTROL DEVICE

摘要

PURPOSE: An automatic gain control device is provided to reduce a ratio of a maximum value to a minimum value of an input signal. CONSTITUTION: The first reference value comparator(1) compares an amplitude of an input signal with the first reference value. A switch(3) supplies a differential amplification degree when the input signal is higher than the first reference value. A subtraction part(4) substrates an output of the switch from a total amplification degree. A variable amplifier(5) duplicates the input signal by a nonlinear amplification degree, and an analog-to-digital converter(6) samples the amplified input signal by a conversion period. An average value calculator(7) calculates an average value of an output signal of the analog-to-digital converter and determines the total amplification degree from the calculated average value so as to be supplied to the subtraction part. The second reference value comparator(9) compares an output of the analog-to-digital converter with the second reference value and supplies an output of the analog-to-digital converter to a next stage when the output of the analog-to-digital converter is higher than the second reference value. A divider(10) the output of the analog-to-digital converter by an output of the average value calculator when the output of the analog-to-digital converter is higher than the second reference value. A multiplier(11) multiplies a digital value of the differential amplification degree by an output of the divider, and an adder(13) adds the output of the analog-to-digital converter and an output of the multiplier.