The method of the power amplifier, the power amplifier

Power amplifier of the present invention includes a MOS transistor (1) a gate length is 180nm or less, the connected output side matching circuit to the drain terminal of the MOS transistor (1) (5), a. Also, MOS transistor (1), the voltage Vd_n standardized by the voltage values ​​which can be allowed in DC state is 0.5 to 0.9, the Vd_n drain - is applied as a source voltage. Moreover, an output matching circuit from the drain terminal normalized by the gate width W (mm) of the load impedance viewed (5) MOS transistor (1) is ZL (= RL + j · XL), the real part of the ZL (RL ) is, RL> in 0.64 × Vd_n + 0.19 (Ω · mm), and a RL <0.64 × Vd_n + 1.73 (Ω · mm).