# US 2014/0191804 A1 · Variable gain amplifier > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191804 A1 - Document ID: US20140191804A1 - Status: Published application - Kind: A1 - Application number: 14/131,819 - Filed: 2012-12-05 - Published: 2014-07-10 - Earliest claimed: 2011-12-20 - Assignees: Panasonic Corporation - Applicants: Panasonic Corporation - Inventors: Ryo Kitamura - Web page: https://patentgrep.com/patent/US20140191804A1 ## CPC - H03F 3/193: with field-effect devices (H03F3/195 takes precedence) - H03F 1/56: Modifications of input or output impedances, not otherwise provided for - H03F 3/45179: {using MOSFET transistors as the active amplifying circuit (H03F3/45278 takes precedence)} - H03G 3/008: {Control by switched capacitors} - H03G 9/14: for gain control and tone control - H03F 2203/45394: the AAC of the dif amp comprising FETs whose sources are not coupled, i.e. the AAC being a pseudo-differential amplifier - H03F: AMPLIFIERS - H03G: CONTROL OF AMPLIFICATION ## Abstract A variable gain amplifier (100) includes a transistor (110), an FB impedance section (120), a source impedance section (130), a drain impedance section (140), a gain controller (150), and a frequency characteristic controller (160). The gain controller (150) varies impedance of one of the FB impedance section (140), the source impedance section (130), and the drain impedance section (140), and outputs a gain control signal. The frequency characteristic controller (160) varies the impedance of different impedance section, based on the gain control signal. ## Claims ### Claim at position 1 1-11. (canceled) ### Claim 12 A variable gain amplifier comprising: an amplifying element including a control terminal to which an input signal is input, a reference-side terminal connected to reference electric-potential, and a power-supply-side terminal connected to a direct-current power supply, the amplifying element configured to amplify the input signal; an FB impedance section connected between the control terminal and the power-supply-side terminal; a reference-side impedance section connected to the reference-side terminal; a power-supply-side impedance section connected to the power-supply-side terminal; a gain controller configured to control a gain of the amplifying element; and a frequency characteristic controller configured to control a frequency characteristic of the gain, wherein the gain controller varies an impedance of one impedance section of the FB impedance section, the reference-side impedance section, and the power-supply-side impedance section, and outputs a control signal for controlling the gain, and the frequency characteristic controller varies an impedance of an impedance section differing from the one impedance section, based on the control signal for controlling the gain. ### Claim 13 (depends on 12) The variable gain amplifier according to claim 12, wherein at least one impedance section of the FB impedance section, the reference-side impedance section, and the power-supply-side impedance section includes at least one switch, and the gain controller changes the switch between ON and OFF of at least one impedance section of the FB impedance section, the reference-side impedance section, and the power-supply-side impedance section. ### Claim 14 (depends on 12) The variable gain amplifier according to claim 12, wherein at least one impedance section of the FB impedance section, the reference-side impedance section, and the power-supply-side impedance section includes a variable capacitor, and the frequency characteristic controller varies the variable capacitor of at least one impedance section of the FB impedance section, the reference-side impedance section, and the power-supply-side impedance section. ### Claim 15 (depends on 14) The variable gain amplifier according to claim 14, further comprising: a table which defines a gain parameter included in the control signal and a capacitance value of the variable capacitor, which corresponds to the gain parameter, wherein the frequency characteristic controller varies the variable capacitor of at least one impedance section of the FB impedance section, the reference-side impedance section, and the power-supply-side impedance section, the variable capacitor being varied into a capacitance value of the variable capacitor corresponding to the gain parameter. ### Claim 16 (depends on 14) The variable gain amplifier according to claim 14, wherein the gain controller changes the switch between ON and OFF of the power-supply-side impedance section, and the frequency characteristic controller varies the variable capacitor of the reference-side impedance section. ### Claim 17 (depends on 14) The variable gain amplifier according to claim 14, wherein the gain controller changes the switch between ON and OFF of the reference-side impedance section, and the frequency characteristic controller varies the variable capacitor of the FB impedance section. ### Claim 18 (depends on 14) The variable gain amplifier according to claim 14, wherein the gain controller changes the switch between ON and OFF of the reference-side impedance section, and the frequency characteristic controller varies the variable capacitor of the power-supply-side impedance section. ### Claim 19 (depends on 14) The variable gain amplifier according to claim 14, wherein the gain controller varies the switch between ON and OFF of the FB impedance section and varies the switch between ON and OFF of the reference-side impedance section, and the frequency characteristic controller varies the variable capacitor of the reference-side impedance section in correspondence to change of the switch between ON and OFF of the FB impedance section, and varies the variable capacitor of the power-supply-side impedance section in correspondence to change of the switch between ON and OFF of the reference-side impedance section. ### Claim 20 (depends on 14) The variable gain amplifier according to claim 14, further comprising: a second amplifying element including a second control terminal to which an output signal from the amplifying element is input, a second reference-side terminal connected to the reference electric-potential, and a second power-supply-side terminal connected to the direct-current power supply, the second amplifying element configured to amplify the output signal from the amplifying element; a second FB impedance section connected between the second control terminal and the second power-supply-side terminal and including at least one switch; and a second power-supply-side impedance section connected to the second power-supply-side terminal and including a variable capacitance, wherein the gain controller changes the switch between ON and OFF of the reference-side impedance section and changes the switch between ON and OFF of the second FB impedance section, and the frequency characteristic controller varies the variable capacitor of each of the power-supply-side impedance section and the second power-supply-side impedance section in correspondence to change of the switch between ON and OFF of the reference-side impedance section, and the frequency characteristic controller varies the variable capacitor of the reference-side impedance section in correspondence to change of the switch between ON and OFF of the second FB impedance section. ### Claim 21 (depends on 12) The variable gain amplifier according to claim 12, further comprising: a third-amplifying element including a third control terminal to which a second input signal, which indicates a differential input signal with respect to the input signal, is input, a third reference-side signal connected to the reference electric-potential, and a third power-supply-side terminal connected to the direct-current power supply, the amplifying element and the third-amplifying element form a differential pair; a third FB impedance section connected between the third control terminal and the third power-supply-side terminal and including at least one switch; and a third reference-side impedance section connected to the third reference-side terminal and including a variable capacitor, wherein the gain controller changes the switch between ON and OFF of the FB impedance section and changes the switch between ON and OFF of the third FB impedance section, and the frequency characteristic controller varies the variable capacitor of the reference-side impedance section in correspondence to change of the switch between ON and OFF of the FB impedance section and varies the variable capacitor of the third reference-side impedance section in correspondence to change of the switch between ON and OFF of the third FB impedance section. ### Claim 22 (depends on 12) The variable gain amplifier according to claim 12, further comprising: a third-amplifying element including a third control terminal to which a second input signal, which indicates a differential input signal with respect to the input signal, is input, a third reference-side signal connected to the reference electric-potential, and a third power-supply-side terminal connected to the direct-current power supply, the amplifying element and the third-amplifying element form a differential pair; and a third FB impedance section connected between the third control terminal and the third power-supply-side terminal and including at least one switch, wherein the reference-side impedance section is configured to connect the variable capacity of the reference-side impedance section to the reference-side terminal and the third reference-side terminal, the gain controller changes the switch between ON and OFF of the FB impedance section and changes the switch between ON and OFF of the third FB impedance section, and the frequency characteristic controller varies the variable capacitor of the reference-side impedance section in correspondence to change of the switch between ON and OFF of each of the FB impedance section and the third FB impedance section.