| 摘要 |
PURPOSE: An automatic gain control circuit is described, which can automatically control output gain. CONSTITUTION: The automatic gain control circuit comprises a voltage controlled amplifier amplifying an input signal on the basis of a BIOS voltage and responding to a predetermined control voltage to control and then output gain of the amplified signal, a comparator comparing an output of the voltage control amplifier with a reference voltage to output the compared result as a square wave signal of a high or a low level, a clock input unit combining a square wave signal and an up-clock signal or a down-clock signal to generate a counting input signal, a counter responding to a counting input signal to up-count or down-count and then to output the up-counted or down-counted result as a digital signal of N(>0)bit, and a digital-to-analog converter converting the counted digital signal into an analog voltage to output the converted result as a control voltage. Thus, it is possible to implement gain of an amplifier in one chip by a comparator and a digital-to-analog converter without a great capacitance capacitor added to an exterior of a chip for controlling the gain, thereby reducing a chip size.
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