Patent ID: 7795978

Claim:
A programmable gain circuit comprising: an amplification unit amplifying an input signal; an input resistor coupled to an input terminal of the amplification unit; a feedback resistor coupled between an output terminal of the amplification unit and the input terminal of the amplification unit; a first switch switching a resistance value of the feedback resistor; a second switch switching a resistance value of the input resistor; a control unit controlling the second switch such that the second switch switches the resistance value of the input resistor when the first switch switches the resistance value of the feedback resistor; a plurality of resistors coupled in series with each other as the feedback resistor; a plurality of the first switches corresponding to each of the plurality of the resistors and coupled in parallel thereto; and a group of switches including a plurality of the second switches coupled between the input terminal of the amplification unit and the input resistor canceling an ON-resistance of the first switch, wherein the plurality of the second switches are selected such that the ON-resistance of the selected first switch is canceled, wherein the first switch is coupled in parallel to the feedback resistor, and wherein the second switch is coupled between the input resistor and the input terminal of the amplification unit.