Patent ID: 6259321
Filing Date: 2001-07-10
Classification: H03F,H03G

Abstract:
A CMOS variable gain amplifier comprising:an amplifier having a plurality of variable gain amplifier cells with substantially the same gains connected in series to continuously have a broad gain variation; anda control voltage generator for generating a control voltage of the variable gain amplifier cells to vary a gain of the amplifier by an external control voltage which is regulated according to input voltages and outputting the control voltage, wherein the control voltage generator comprises:an exponential function voltage generator for generating a voltage in the form of an exponential function according to a control input voltage, a variable gain amplifier cell for amplifying an output voltage of the exponential function voltage generator;a current source connected to an output node of the cariable gain amplifier cell for providing a current in the direction of offsetting an output voltage of the variable gain amplifier cell, andan operational amplifier for receiving the offset voltage by the current source and generating the control voltage of the variable gain amplifier cells.