A power amplifier circuit includes an amplifier transistor having a base, a collector, a bias circuit, and a first resistance element connected between the base of the amplifier transistor and the bias circuit. The bias circuit includes a voltage generation circuit, a first transistor having a base to which a first direct-current voltage is supplied, and an emitter from which the bias current or voltage is supplied, a second transistor having a base to which a second direct-current voltage is supplied, and an emitter connected to the emitter of the first transistor, a signal supply circuit disposed between the base of the amplifier transistor and the base of the second transistor, and an impedance circuit disposed between the base of the first transistor and the base of the second transistor.

A power amplifier circuit includes an amplifier transistor having a base, a collector, a bias circuit, and a first resistance element connected between the base of the amplifier transistor and the bias circuit. The bias circuit includes a voltage generation circuit, a first transistor having a base to which a first direct-current voltage is supplied, and an emitter from which the bias current or voltage is supplied, a second transistor having a base to which a second direct-current voltage is supplied, and an emitter connected to the emitter of the first transistor, a signal supply circuit disposed between the base of the amplifier transistor and the base of the second transistor, and an impedance circuit disposed between the base of the first transistor and the base of the second transistor.

A symbol power tracking amplification system including: a modem to generate data and symbol tracking signals; a symbol tracking modulator including a control circuit, first and second voltage supply circuits and a switch circuit, the control circuit generates first and second voltage level control signals in response to the symbol tracking signal, the first voltage supply circuit generates a first output voltage in response to the first voltage level control signal, the second voltage supply circuit generates a second output voltage in response to the second voltage level control signal and the switch circuit outputs the first or second output voltages as a supply voltage in response to a switch control signal; an RF block to generate an RF signal based on the data signal from the modem; and a power amplifier to adjust a power level of the RF signal based on the supply voltage.

A symbol power tracking amplification system including: a modem to generate data and symbol tracking signals; a symbol tracking modulator including a control circuit, first and second voltage supply circuits and a switch circuit, the control circuit generates first and second voltage level control signals in response to the symbol tracking signal, the first voltage supply circuit generates a first output voltage in response to the first voltage level control signal, the second voltage supply circuit generates a second output voltage in response to the second voltage level control signal and the switch circuit outputs the first or second output voltages as a supply voltage in response to a switch control signal; an RF block to generate an RF signal based on the data signal from the modem; and a power amplifier to adjust a power level of the RF signal based on the supply voltage.

A N-path filter includes a plurality of switch-capacitor circuits controlled by a plurality of logical signals, respectively, and joined at a common shunt node, each of said switch-capacitor circuit comprising: a respective switch configured to controllably connect the common shunt node to a respective middle node in accordance with a respective logical signals among said plurality of logical signals; and a respective balanced MOS (metal oxide semiconductor) capacitor connected to the respective middle node, wherein the respective balanced MOS capacitor exhibits a capacitance at the respective middle node with reference to a power supply node and a ground node.

A high-frequency signal transmission-reception circuit includes a plurality of band pass filter groups each including a plurality of band pass filter pairs; a first switch including a plurality of band pass filter-side terminal groups each including a plurality of band pass filter-side terminals, and an antenna-side terminal group; a plurality of couplers configured to output respective signal strengths of high-frequency signals transmitted on a plurality of transmission paths; and a second switch including an input terminal group electrically connected to the plurality of couplers, and an output terminal configured to output a detection signal output from one of the plurality of couplers. The first switch electrically connects one band pass filter-side terminal in one band pass filter-side terminal group and one antenna-side terminal, and also electrically connects one band pass filter-side terminal in another band pass filter-side terminal group and another antenna-side terminal.

A high-frequency signal transmission-reception circuit includes a plurality of band pass filter groups each including a plurality of band pass filter pairs; a first switch including a plurality of band pass filter-side terminal groups each including a plurality of band pass filter-side terminals, and an antenna-side terminal group; a plurality of couplers configured to output respective signal strengths of high-frequency signals transmitted on a plurality of transmission paths; and a second switch including an input terminal group electrically connected to the plurality of couplers, and an output terminal configured to output a detection signal output from one of the plurality of couplers. The first switch electrically connects one band pass filter-side terminal in one band pass filter-side terminal group and one antenna-side terminal, and also electrically connects one band pass filter-side terminal in another band pass filter-side terminal group and another antenna-side terminal.

An amplifier circuit is configured in such a way that the amplifier circuit includes: a first amplifier to amplify a signal to be amplified; an output matching circuit through which the signal amplified by the first amplifier propagates; and a second amplifier to amplify the signal which has propagated through the output matching circuit, and the output matching circuit is a lumped constant circuit including multiple lumped constant elements, and, by using the multiple lumped constant elements, transforms the impedance seen on the second amplifier side from the first amplifier when the output power of the second amplifier is lower than saturation electric power, to impedance higher than impedance seen on the second amplifier side from the first amplifier when the output power of the second amplifier is equal to the saturation electric power.

An outphasing amplifier includes a first amplifier configured to amplify a first signal, a second amplifier configured to amplify a second signal of which a phase difference from the first signal changes, and a synthesizer that has a first transmission line through which a third signal output from the first amplifier passes, a second transmission line through which a fourth signal output from the second amplifier passes, a first coupling circuit that is separately provided from the first transmission line and is coupled to the first transmission line, a second coupling circuit that is separately provided from the second transmission line and coupled to the second transmission line, and a node that synthesizes the third signal having passed through the first transmission line and the fourth signal having passed through the second transmission line.

An outphasing amplifier includes a first amplifier configured to amplify a first signal, a second amplifier configured to amplify a second signal of which a phase difference from the first signal changes, and a synthesizer that has a first transmission line through which a third signal output from the first amplifier passes, a second transmission line through which a fourth signal output from the second amplifier passes, a first coupling circuit that is separately provided from the first transmission line and is coupled to the first transmission line, a second coupling circuit that is separately provided from the second transmission line and coupled to the second transmission line, and a node that synthesizes the third signal having passed through the first transmission line and the fourth signal having passed through the second transmission line.