| 摘要 |
PURPOSE:To attain the miniaturization and high efficiency of a power amplifier in an analog/digital shared telephone system by letting it be an operation variable type amplifier by switching the gate voltage and drain voltage of the amplifier, and performing a saturated operation or a linear operation. CONSTITUTION:A switch 1-2 is switched by an operation switching control signal, and the output voltage of a saturation type operating gate voltage setting circuit 1-3 is supplied to a operation variable type power amplifier 1-1 as a gate voltage at the time of an analog system, and the output voltage of a linear operating gate voltage setting circuit 1-4 is supplied to the power amplifier 1-1 as the gate voltage at the time of a digital system. At the same time, the output voltage of a saturation type operating drain voltage setting circuit 1-6 is supplied as a drain voltage at the time of the analog system, and the output voltage of a linear operating drain voltage setting circuit 1-5 is supplied as the drain voltage at the time of the digital system. Thus, one operation variable amplifier can be shared with the analog/digital systems, and the miniaturization and high efficiency of the power amplifier can be attained. |
