Matsushita Electric Industrial Co., Ltd.

Kazuhiko Ohhashi

Kaname Motoyoshi

Masahiko Inamori

Hiroshi Sugiyama

Masao Nakayama

A bias voltage is applied via a first resistance to the base of a first transistor, and a radio frequency signal is input via a first capacitor to the base of the first transistor. The bias voltage is applied via a second resistance to the base of a second transistor. The bias voltage is applied via a third resistance to the base of a third transistor, and the radio frequency signal RF is input via a third capacitor to the base of the third transistor. A first band rejection filter is provided between the base of the first transistor and the base of the second transistor. A second band rejection filter is provided between the base of the second transistor and the base of the third transistor. The collectors of the first to third transistors are connected in common and the emitters thereof are all grounded.

Radio frequency power amplifier

A bias current to be supplied to an amplification circuitis drawn out of a collector of a transistor Qof a bias circuit. The drawn-out bias current is input to a base of a transistor Qvia an attenuation filter Fand is output from an emitter of the transistor Qin the state where the voltage thereof is reduced by a level corresponding to Vbe. The attenuation filter Fis conducted in a DC manner, and attenuates a component of a frequency fH(=2ft&#x2212;fr) defined by a transmission frequency ft and a receiving frequency fr of a radio frequency signal. The bias current output from the emitter of the transistor Qis supplied to the amplification circuitvia an attenuation filter F. The attenuation filter Fis conducted in a DC manner, and attenuates a component of a frequency fL(=|fr&#x2212;ft|).

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Kyoto, Japan

Kazuhiko Ohhashi