| 摘要 |
A mobile station (10) is constructed to include transmitter circuitry (20) and an antenna (24) for transmitting a signal. The transmitter circuitry includes a multistage power amplifier (1) having a first power amplifier stage (1A) with an output coupled to an input of a second power amplifier stage (1B). The output of the second power amplifier stage is coupled to the antenna. The transmitter circuitry further includes a source of variable bias current (3) that is input to the second power amplifier stage for controlling the gain thereof, a source of fixed bias current (3C), and a summing junction (3E) for summing the fixed bias current and the variable bias current for input to the first power amplifier stage for controlling the gain thereof. The gain of the first power amplifier stage is controlled such that a minimum desired gain of the second power amplifier stage is achieved without inducing a collapse in the gain of the first power amplifier stage. The transmitter circuitry may further include a circuit block (3D) coupled in series with the source of fixed bias current for selectively turning off the fixed bias current.
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