VARIABLE GAIN AMPLIFICATION CIRCUIT FOR AUTOMATIC GAIN CONTROL IN MOBILE COMMUNICATION TERMINAL EQUIPMENT

摘要

PURPOSE: A variable gain amplification circuit for an automatic gain control in mobile communication terminal equipment is provided to control linearly a gain to according to a control voltage by using a variable gain amplification circuit. CONSTITUTION: A variable gain amplification circuit for an automatic gain control in mobile communication terminal equipment comprises a source part and a load part. The source part comprises an input MOSFET including a differential pair, one more MOSFET used as a resistance, a MOSFET used as a current source. The load part comprises one more MOSFET used as a resistance and a MOSFET used as a current source. A transconductance of the input MOSFET of the source part is smaller than the transconductance of the MOSFET used as the resistance of the load part. A control voltage increases a gate voltage of the MOSFET used as the resistance of the source part and decreases a gate voltage of the MOSFET used as the resistance of the load part.