| 摘要 |
<p>A controlled-output power amplifier (50) is provided having a wide dynamic range in a plurality of output power levels. The controlled-output amplifier (50) includes an amplifier (12) for receiving an input signal (14) and for providing an output signal (16) therefrom. A power detector (24) is employed for rectifying a sample signal and providing a DC output signal (26) therefrom. An active variable coupling network (52) which preferably includes a varactor (62) is connected between the output of the amplifier (12) and the power detector (24). The variable coupling network (52) receives the amplifier output signal (16) and further receives an isolation voltage (54) and adjusts the amount of isolation between the amplifier (12) and the power detector (24). For high output signals, the isolation voltage (54) causes a high isolation thereby causing less power to be transferred to the power detector (24). The isolation voltage (54), similarly, decreases the isolation for low output signals such that more power is transferred to the power detector (24). The DC output signal (26) is then compared with a fixed voltage reference (30). The voltage comparison provides an error voltage (34) which is used to adjust the gain of amplifier (12) so that the output signal (16) of the amplifier (12) is set to a desired magnitude. <IMAGE></p> |
