AUTOMATIC GAIN CONTROL CIRCUIT FOR MOBILE RECEIVER CAPABLE OF PREVENTING DISTORTION IN OUTPUT SIGNAL BY REDUCING GAIN OF VARIABLE AMPLIFIER WHEN LARGE SIGNAL IS RECEIVED, AMPLIFYING CIRCUIT AND INTEGRATED CIRCUIT HAVING THE AUTOMATIC GAIN CONTROL CIRCUIT, AND AUTOMATIC GAIN CONTROL METHOD FOR MOBILE RECEIVER

摘要

PURPOSE: An automatic gain control circuit for mobile receiver, an amplifying circuit and an integrated circuit having the automatic gain control circuit, and an automatic gain control method for the mobile receiver are provided to prevent distortion in an output signal by reducing gain of a variable amplifier when a large signal is received. CONSTITUTION: An automatic gain control circuit controls a gain of a variable amplifier which amplifies received signals from an antenna from a mobile member and outputs the result. The circuit includes magnitude detectors(Det1,Det2), comparators(CO1,CO2), and a controller. The comparators compare a result of the magnitude detectors with first and second threshold voltages. The controller outputs a control signal based on the compared result. The second threshold voltage is greater than the first threshold voltage. The controller outputs the control signal to rapidly increase the gain of the variable amplifier when the result of the comparators is slowly increased. The controller outputs the control signal to rapidly decrease the gain of the variable amplifier when the result of the comparators is slowly decreased.