# US 2021/0242843 A1 · Power amplifier circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0242843 A1 - Document ID: US20210242843A1 - Status: Published application - Kind: A1 - Application number: 17/238,835 - Filed: 2021-04-23 - Published: 2021-08-05 - Earliest claimed: 2018-05-21 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Takayuki TSUTSUI; Masao KONDO; Satoshi TANAKA - Web page: https://patentgrep.com/patent/US20210242843A1 ## CPC - H03F 3/245: {with semiconductor devices only} - H03F 1/0261: {with control of the polarisation voltage or current, e.g. gliding Class A} - H03F 1/0266: {by using a signal derived from the input signal} - H03F 1/301: {in MOSFET amplifiers (H03F1/303, H03F1/305, H03F1/308 take precedence)} - H03F 1/302: {in bipolar transistor amplifiers (H03F1/303, H03F1/305, H03F1/307 take precedence)} - H03F 1/56: Modifications of input or output impedances, not otherwise provided for - H03F 3/04: with semiconductor devices only - H03F 3/19: with semiconductor devices only - H03F 3/193: with field-effect devices (H03F3/195 takes precedence) - H03F 3/21: with semiconductor devices only {(H03F3/245 takes precedence)} - H03F 2200/411: the output amplifying stage of an amplifier comprising two power stages - H03F 2200/451: the amplifier being a radio frequency amplifier - H03F: AMPLIFIERS ## Abstract A power amplifier circuit includes a first transistor that amplifies a first signal and outputs a second signal; a second transistor that amplifies the second signal and outputs a third signal; a bias circuit that supplies a bias current to a base of the second transistor; and a bias adjustment circuit that adjusts the bias current by subjecting the first signal to detection. The bias adjustment circuit controls the bias current such that a first current extracted from the bias circuit depends on a magnitude of the first signal. ## Claims ### Claim 1 A power amplifier circuit comprising: a first transistor configured to amplify a first signal and output a second signal; a second transistor configured to amplify the second signal and output a third signal; a bias circuit configured to supply a bias current to a base of the second transistor; and a bias adjustment circuit configured to adjust the bias current by subjecting the first signal to detection, wherein the bias adjustment circuit controls the bias current such that a first current extracted from the bias circuit depends on a magnitude of the first signal, wherein the bias circuit includes: a first resistance element having one end to which a bias control voltage is supplied, and a third transistor having a base connected to another end of the first resistance element and an emitter from which the bias current is outputted, and wherein the first current is extracted from the base of the third transistor. ### Claim 2 (depends on 1) The power amplifier circuit according to claim 1, wherein an emitter of the first transistor is connected to ground. ### Claim 3 (depends on 1) The power amplifier circuit according to claim 1, wherein the bias adjustment circuit includes a first diode having an anode connected to a side on which a supply path of the first signal to the first transistor is disposed and to a base side of the third transistor, and having a cathode connected to a ground side. ### Claim 4 (depends on 3) The power amplifier circuit according to claim 3, wherein the first diode is a fourth transistor that has a collector connected to the side on which the supply path of the first signal to the first transistor is disposed, a base connected to the base side of the third transistor, and an emitter connected to the ground side, the fourth transistor being diode connected. ### Claim 5 (depends on 3) The power amplifier circuit according to claim 3, wherein the bias adjustment circuit further includes a second diode having an anode connected to the base of the third transistor and a cathode connected to the anode of the first diode. ### Claim 6 (depends on 4) The power amplifier circuit according to claim 4, wherein the bias adjustment circuit further includes a second diode having an anode connected to the base of the third transistor and a cathode connected to the anode of the first diode. ### Claim 7 (depends on 5) The power amplifier circuit according to claim 5, wherein the second diode is a fifth transistor that has a collector connected to the base of the third transistor and an emitter connected to the anode of the first diode, the fifth transistor being diode connected. ### Claim 8 (depends on 3) The power amplifier circuit according to claim 3, wherein the bias adjustment circuit further includes a filter circuit having one end connected to the anode of the first diode and another end connected to the base side of the third transistor. ### Claim 9 (depends on 4) The power amplifier circuit according to claim 4, wherein the bias adjustment circuit further includes a filter circuit having one end connected to the anode of the first diode and another end connected to the base side of the third transistor. ### Claim 10 (depends on 8) The power amplifier circuit according to claim 8, wherein the bias adjustment circuit further includes a second diode having an anode connected to the base of the third transistor and a cathode connected to the filter circuit. ### Claim 11 (depends on 8) The power amplifier circuit according to claim 8, wherein the filter circuit includes a first capacitor having one end connected to the anode of the first diode and another end grounded, and a second resistance element having one end connected to the anode of the first diode and to the one end of the first capacitor, and having another end connected to the base side of the third transistor. ### Claim 12 (depends on 8) The power amplifier circuit according to claim 8, wherein the bias adjustment circuit further includes a second diode having an anode connected to the base of the third transistor and a cathode connected to the filter circuit, and wherein the filter circuit includes a first capacitor having one end connected to the anode of the first diode and another end grounded, and a second resistance element having one end connected to the anode of the first diode and to the one end of the first capacitor, and having another end connected to the cathode of the second diode. ### Claim 13 A power amplifier circuit comprising: a first transistor configured to amplify a first signal and output a second signal; a second transistor configured to amplify the second signal and output a third signal; a bias circuit configured to supply a bias current to a base of the second transistor; and a bias adjustment circuit configured to adjust the bias current by subjecting the first signal to detection, wherein the bias adjustment circuit controls the bias current such that a first current extracted from the bias circuit depends on a magnitude of the first signal, wherein the bias circuit includes: a resistance element connected in series with an inductor and a second capacitor, the inductor and the second capacitor being connected in parallel to each other. ### Claim 14 (depends on 13) The power amplifier circuit according to claim 13, wherein one end of the resistance element is connected to the inductor and the second capacitor connected in parallel to each other, and another end of the resistance element is connected to the base of the second transistor. ### Claim 15 (depends on 13) The power amplifier circuit according to claim 13, wherein the inductor and the second capacitor connected in parallel to each other are connected to an emitter of a third transistor. ### Claim 16 (depends on 13) The power amplifier circuit according to claim 13, wherein the first transistor has an emitter connected to ground. ### Claim 17 (depends on 13) The power amplifier circuit according to claim 13, wherein the bias adjustment circuit includes a first diode having an anode connected to a side on which a supply path of the first signal to the first transistor is disposed and to a base side of the third transistor, and having a cathode connected to a ground side. ### Claim 18 (depends on 17) The power amplifier circuit according to claim 17, wherein the first diode is a fourth transistor that has a collector connected to the side on which the supply path of the first signal to the first transistor is disposed, a base connected to the base side of the third transistor, and an emitter connected to the ground side, the fourth transistor being diode connected. ### Claim 19 (depends on 13) The power amplifier circuit according to claim 13, wherein the bias adjustment circuit further includes a second diode having an anode connected to the base of the third transistor and a cathode connected to the anode of the first diode. ### Claim 20 (depends on 17) The power amplifier circuit according to claim 17, wherein the bias adjustment circuit further includes a filter circuit having one end connected to the anode of the first diode and another end connected to the base side of the third transistor.