Patent ID: 7127224

Claim:
A base band circuit for producing an output base band signal from an input base band signal, comprising: a first low pass filter circuit supplied at an input port thereof with said input base band signal for restricting a frequency band of said input base band signal, and outputting a filtrate signal from an output port thereof; a series of variable gain amplifiers forming a series circuit together with said first low pass filter, and responsive to an internal gain control signal indicating a gain to be achieved so as to produce said output base band signal from said filtrate signal at an output port of said series circuit through an amplification at said gain; and a feedback loop connected between said output port of said series circuit and an input port of said series circuit, and including a direct current component extracting circuit that continuously attenuates said output base band signal with an attenuation factor corresponding to said gain and extracts a direct current component from said output base band signal and an eliminating circuit eliminating said direct current component from said input base band signal.