Patent ID: 6563383
Filing Date: 2003-05-13
Classification: H03F,H03G

Abstract:
A variable gain circuit comprising:a variable gain amplifier which receives an input signal outputs an amplified signal, and includes a first field-effect transistor; a gain control signal compensation circuit which outputs a gain control signal for controlling a gain of said variable gain amplifier and includes a second field-effect transistor; a gain deviation correction circuit which corrects a gain deviation based on said variable gain amplifier and said gain control signal compensation circuit; and a gain control signal converter which converts an external gain control signal into an internal gain control signal, said variable gain amplifier including the first field-effect transistor being a first variable gain amplifier, the first gain control signal being a first gain control signal, said gain control signal compensation circuit including the second field-effect transistor being a first gain control signal compensation circuit, said gain deviation correction circuit including a second gain control signal compensation circuit and a second variable gain amplifier, said first gain control signal compensation circuit converting the internal gain control signal into the first gain control signal and inputting the first gain control signal to said first variable gain amplifier to control gain of said first variable gain amplifier, and said second gain control signal compensation circuit converting the internal gain control signal into the second gain control signal and inputs the second gain control signal to said second variable gain amplifier (201) to control gain of said second variable gain amplifier.