An impedance matching network for a radio frequency, RF, amplifier device, the impedance matching network having a parallel branch comprising: a baseband termination circuit having reactive components configured to present low impedance to signals in a baseband frequency range that is below a fundamental frequency range associated with the RF amplifier device; a fundamental frequency matching circuit having reactive components configured to substantially match an output impedance of the RF amplifier device in the fundamental frequency range to a predetermined value; and a second-order harmonic termination circuit having reactive components configured to present low impedance at second order harmonics of RF signals having a fundamental frequency in the fundamental frequency range, wherein the fundamental frequency matching circuit comprises a first capacitor and a first inductor that are electrically coupled in series; a capacitance of the first capacitor is such that the first capacitor appears as a short at frequencies in the fundamental frequency range; and an inductance of the first inductor is such that the first inductor and an intrinsic capacitance of the RF amplifier device form a parallel LC resonator at frequencies in the fundamental frequency range; wherein the second-order harmonic termination circuit comprises a parallel LC resonator connected in series between the first inductor and the first capacitor of the fundamental frequency matching circuit; the parallel LC resonator comprises a second capacitor that is in parallel with a second inductor; an inductance of the second inductor and a capacitance of the second capacitor are such that the parallel LC resonator, together with the first inductor and the intrinsic capacitance of the RF amplifier device, resonates at second order harmonics of fundamental frequencies in the fundamental frequency range; wherein the baseband termination circuit comprises a third capacitor and a third inductor connected in series and electrically coupled to the first capacitor and the second-order harmonic termination circuit; an inductance of the third inductor and a capacitance of the third capacitor are such that the third inductor and the third capacitor provide low impedance to signals in the baseband frequency range; and wherein the parallel LC resonator, the first capacitor, the third inductor, and the third capacitor are provided in an integrated passive device. a baseband termination circuit having reactive components configured to present low impedance to signals in a baseband frequency range that is below a fundamental frequency range associated with the RF amplifier device; a fundamental frequency matching circuit having reactive components configured to substantially match an output impedance of the RF amplifier device in the fundamental frequency range to a predetermined value; and a second-order harmonic termination circuit having reactive components configured to present low impedance at second order harmonics of RF signals having a fundamental frequency in the fundamental frequency range, wherein the fundamental frequency matching circuit comprises a first capacitor and a first inductor that are electrically coupled in series; a capacitance of the first capacitor is such that the first capacitor appears as a short at frequencies in the fundamental frequency range; and an inductance of the first inductor is such that the first inductor and an intrinsic capacitance of the RF amplifier device form a parallel LC resonator at frequencies in the fundamental frequency range; a capacitance of the first capacitor is such that the first capacitor appears as a short at frequencies in the fundamental frequency range; and an inductance of the first inductor is such that the first inductor and an intrinsic capacitance of the RF amplifier device form a parallel LC resonator at frequencies in the fundamental frequency range; wherein the second-order harmonic termination circuit comprises a parallel LC resonator connected in series between the first inductor and the first capacitor of the fundamental frequency matching circuit; the parallel LC resonator comprises a second capacitor that is in parallel with a second inductor; an inductance of the second inductor and a capacitance of the second capacitor are such that the parallel LC resonator, together with the first inductor and the intrinsic capacitance of the RF amplifier device, resonates at second order harmonics of fundamental frequencies in the fundamental frequency range; the parallel LC resonator comprises a second capacitor that is in parallel with a second inductor; an inductance of the second inductor and a capacitance of the second capacitor are such that the parallel LC resonator, together with the first inductor and the intrinsic capacitance of the RF amplifier device, resonates at second order harmonics of fundamental frequencies in the fundamental frequency range; wherein the baseband termination circuit comprises a third capacitor and a third inductor connected in series and electrically coupled to the first capacitor and the second-order harmonic termination circuit; an inductance of the third inductor and a capacitance of the third capacitor are such that the third inductor and the third capacitor provide low impedance to signals in the baseband frequency range; and wherein the parallel LC resonator, the first capacitor, the third inductor, and the third capacitor are provided in an integrated passive device.