| 摘要 |
A power amplifier circuit arrangement particularly useful for portable phones used in wireless systems. A power amplifier stage can be partially or completely bypassed so that multi-stage amplifiers can be built that allow wide dynamic range of power amplification to be obtained efficiently. A switch at the input of an amplifier stage couples an input signal either to an amplifier or to a bypass path. The output of the amplifier is coupled to a first impedance-transforming network. The bypass path includes a second impedance-transforming network. A third impedance transforming network couples the outputs of the first and second impedance transforming networks. The impedance transforming networks are constructed and arranged so that input and output signals see the correct load regardless of whether the amplifier is used or bypassed. Using the principles of this invention, multi-stage amplifiers can be constructed including input and bypass attenuators to achieve a wide range of gain levels.
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