Variable gain amplifier, correction method and receiving device

A method for attenuating a DC offset voltage generated in a variable gain amplifier including a differential amplifier circuit having an inversion input terminal, a non-inversion input terminal, an inversion output terminal, and a non-inversion output terminal;

• first and second feedback resistors respectively coupled between the inversion output terminal and the non-inversion input terminal and between the non-inversion output terminal and the inversion input terminal;
• and first and second input resistors respectively coupled to the inversion input terminal and the non-inversion input terminal, comprising:
• controlling resistance values of the first and second feedback resistors or resistance values of the first and second input resistors to control a gain;
• outputting a first correction voltage to correct a potential difference generated between a first conductor provided with the first input resistor and a second conductor provided with the second input resistor;
• and
• correcting a potential difference generated between a third conductor coupled to the inversion output terminal and a fourth conductor coupled to the non-inversion output terminal,
• wherein the DC offset voltage includes a first offset voltage which depends on the gain, and a second offset voltage which does not depend on the gain,
• wherein the step of correcting the potential difference includes:
• controlling the gain in such a manner that the first offset voltage becomes sufficiently larger than the second offset voltage;
• and
• setting a potential difference correction amount for attenuating the second offset voltage of the DC offset voltage, and
• wherein the outputting the first correction voltage includes:
• controlling the gain in such a manner that the first offset voltage becomes sufficiently larger than the second offset voltage in a state in which the second offset voltage is attenuated by the potential difference correcting operation;
• and
• setting the first correction voltage so as to attenuate the first offset voltage of the DC offset voltage.

A variable gain amplifier comprising:

• a differential amplifier circuit including an inversion input terminal, a non-inversion input terminal, an inversion output terminal, and a non-inversion output terminal;
• first and second feedback resistors respectively coupled between the inversion output terminal and the non-inversion input terminal and between the non-inversion output terminal and the inversion input terminal;
• first and second input resistors respectively coupled to the inversion input terminal and the non-inversion input terminal;
• a control unit for controlling resistance values of the first and second feedback resistors or resistance values of the first and second input resistors to control a gain;
• a first voltage correction unit coupled to a preceding stage of the first and second input resistors and for outputting a first correction voltage to correct a potential difference generated between a first conductor provided with the first input resistor and a second conductor provided with the second input resistor;
• and
• a second voltage correction unit coupled to the inversion output terminal and the non-inversion output terminal and for correcting a potential difference generated between a third conductor coupled to the inversion output terminal and a fourth conductor coupled to the non-inversion output terminal,
• wherein the control unit is configured to control the first correction voltage and a correction amount of the potential difference by the second voltage correction unit and thereby attenuate a DC offset voltage generated between the inversion output terminal and the non-inversion output terminal, and
• wherein the second voltage correction unit is directly coupled to the inversion output terminal and the non-inversion output terminal.