VARIABLE GAIN AMPLIFIER CIRCUIT WITH PLURAL VARIABLE GAIN AMPLIFIERS HAVING HOMOGENEOUS GAINS AND OPERATIONAL VOLTAGES

摘要

PURPOSE: A variable gain amplifier is provided to suppress difference of gains and operational voltages due to difference of physical characteristics of variable gain amplifiers by dividing input signals applied to the variable gain amplifiers. CONSTITUTION: A first switch(10) divides an input signal into two signals. A first variable gain amplifier(VGA_I) and a second variable gain amplifier(VGA_Q) amplify two divided signal, respectively. A second switch(20) mixes the amplified outputs from the first and second variable gain amplifiers to restore an original signal. A low pass filter is furthered included in the variable gain amplifier circuit to suppress noises generated at the first and second switches.