# US 2013/0154746 A1 · Variable gain amplifier circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0154746 A1 - Document ID: US20130154746A1 - Status: Published application - Kind: A1 - Application number: 13/547,775 - Filed: 2012-07-12 - Published: 2013-06-20 - Earliest claimed: 2011-07-12 - Assignees: NXP B.V. - Inventors: Rob KROSSCHELL - Web page: https://patentgrep.com/patent/US20130154746A1 ## CPC - H03F 3/45: Differential amplifiers (differential sense amplifiers G11C7/062) - H03F 1/22: by use of cascode coupling, i.e. earthed cathode or emitter stage followed by earthed grid or base stage respectively - H03F 3/4508: {using bipolar transistors as the active amplifying circuit (H03F3/45278 takes precedence)} - H03G 1/0023: {in emitter-coupled or cascode amplifiers (H03G1/0029 takes precedence)} - H03G 3/30: in amplifiers having semiconductor devices - H03G 7/08: incorporating negative feedback - H03F 2203/45244: the differential amplifier contains one or more explicit bias circuits, e.g. to bias the tail current sources, to bias the load transistors - H03F 2203/45306: the common gate stage implemented as dif amp eventually for cascode dif amp - H03F: AMPLIFIERS - H03G: CONTROL OF AMPLIFICATION ## Abstract A variable gain amplifier circuit (300) comprising a first transistor (310) and a second transistor (312); and an additional transistor (320). The first transistor (310) and second transistor (312) are arranged as common base transistors. The additional transistor (320) is configured to provide part of a translinear loop with the first (310) and second transistors (310). A current through the conduction channel of the first transistor (310) is configured to contribute to an output of the variable gain amplifier circuit current. The circuit (300) is configured such that a current through the conduction channel of the second transistor (312) is copied to the additional transistor (322). ## Claims ### Claim 1 A variable gain amplifier circuit comprising: a first transistor and a second transistor, wherein the first transistor and second transistor are arranged as common base transistors; and an additional transistor that is configured to provide part of a translinear loop with the first and second transistors; wherein a current through the conduction channel of the first transistor is configured to contribute to an output of the variable gain amplifier circuit current, and the circuit is configured such that a current through the conduction channel of the second transistor is copied to the additional transistor. ### Claim 2 (depends on 1) The circuit of claim 1, wherein the additional transistor is configured such that current flows through its base emitter junction in the opposite way to current that flows through the base emitter junction of the second transistor. ### Claim 3 (depends on 1) The variable gain amplifier circuit of claim 1, comprising a current steering cascode comprising the first transistor and the second transistor. ### Claim 4 (depends on 3) The variable gain amplifier circuit of claim 3, wherein the current steering cascode further comprises a third transistor, wherein the third transistor is arranged as a common emitter transistor. ### Claim 5 (depends on 4) The variable gain amplifier circuit of claim 4, wherein the collector of the third transistor is connected to the emitter of both the first transistor and the second transistor. ### Claim 6 (depends on 1) The circuit of claim 1, further comprising a current minor that is configured to couple the current through the conduction channel of the second transistor to the conduction channel of the additional transistor. ### Claim 7 (depends on 1) The circuit of claim 1, further comprising two current mirrors that are configured to couple the current through the conduction channel of the second transistor to the conduction channel of the additional transistor. ### Claim 8 (depends on 1) The circuit of claim 1, further comprising a voltage source or a circuit with a voltage output that is configured to provide a control voltage for setting the gain of the variable gain amplifier circuit. ### Claim 9 (depends on 8) The circuit of claim 8, further comprising: a current source; and a control transistor that provides part of the translinear loop; wherein the current source is configured to provide a current to the control transistor, the current having a value that has an exponential relationship with respect to the control voltage. ### Claim 10 (depends on 8) The circuit of claim 8, further comprising: a control transistor that provides part of the translinear loop; and a further transistor, wherein the conduction channel of the further transistor is provided in series with the conduction channel of the control transistor; wherein the further transistor is configured to receive the control voltage at its base, and provide a current to the control transistor, the current having a value that has an exponential relationship with respect to the control voltage. ### Claim 11 (depends on 10) The circuit of claim 10, wherein the further transistor is independent of the translinear loop. ### Claim 12 (depends on 1) The circuit of claim 1, wherein the variable gain amplifier circuit includes one or more extra transistors that are configured to form part of the translinear loop, wherein the number of transistors that are arranged as having current flow from base to emitter around the translinear loop is equal to the number of transistors that are arranged as having current flow from emitter to base around the translinear loop. ### Claim 13 (depends on 1) The circuit of claim 1, wherein one or more, or all of the transistors are bipolar junction transistors. ### Claim 14 (depends on 1) An integrated circuit comprising the circuit of claim 1.