RF PA almost working in large signal, so it's circuit design methods and transistor used are different from microwave small signal amplifier, these will led to RF PA design become more difficulty.

射频功率放大器总是工作在大信号状态下，它所用的放大器件和电路设计方法都不同于小信号放大器，导致了功率放大器的设计难度较大。

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The first step in the RF amplifier design is to check if the transistor is unconditionally stable.

微波放大器设计中，首要考虑的问题是管子的稳定性。

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