Patent ID: 7541874

Claim:
A high-frequency power amplifier device comprising: a power amplifier transistor which amplifies a high-frequency signal; an output matching circuit connected to an output side of said power amplifier transistor; an impedance conversion circuit connected to an output side of said output matching circuit; and a high-frequency element connected to an output side of said impedance conversion circuit, wherein said high-frequency power amplifier device is designed so that X[f] satisfies X[L]<X[H], where j denotes an imaginary number, f denotes a frequency, an impedance of said high-frequency element viewed from an output terminal of said output matching circuit is defined as Z[f]=R[f]+jX[f], L denotes a lower limit of the frequency, and H denotes an upper limit of the frequency, Δf/fM is 0.05 or above, where Δf denotes a frequency bandwidth of said high-frequency power amplifier device and fM denotes a center value of the frequency, and said impedance conversion circuit is set so that a voltage standing wave ratio (VSWR) standardized by an impedance of the output side of said power amplifier transistor is smaller than a VSWR of an impedance of the output side of said impedance conversion circuit viewed from an output terminal of said impedance conversion circuit, the impedance of the output side of said power amplifier transistor being viewed from an output terminal of said power amplifier transistor and corresponding to a center value of an impedance of the frequency.