INPUT TERMINAL CIRCUIT OF AUTOMATIC GAIN AMPLIFIER

摘要

PURPOSE: An input terminal circuit of an automatic gain amplifier is provided to design RC filter so as to input a desired control voltage to the automatic gain amplifier by considering an internal resistance component of the automatic gain amplifier. CONSTITUTION: An input terminal circuit of an automatic gain amplifier(100) includes a first resistor, and a condenser. One end of the first resistor(R1) is connected to a signal source for receiving PDM signal, and the other end of the first resistor is connected to the input terminal of the automatic gain amplifier. One end of the condenser(C) is connected to the input terminal, and the other end of the condenser is connected to a ground. The first resistor includes an input terminal inner resistance of the automatic gain amplifier. A capacitance of the condenser is determined by a time constant required by both an interface of the automatic gain amplifier and a signal source(200). A second resistor is positioned between the first resistor and the input terminal.