| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent overdrive of a final stage amplifier by optimizing the amount of drive of a drive stage amplifier over the entire frequency band, and to enhance the efficiency of whole power amplifier. <P>SOLUTION: A drain voltage control circuit 30 controls the drain voltage of a drive stage amplifier 12 so that the amount of back-off of the drive stage amplifier 12 detected from the detection output of a backoff detector 22 has a predetermined value, thus optimizing the drive amount of the drive stage amplifier 12 over the entire frequency band. A variable attenuator control circuit 33 controls attenuation of a variable attenuator 11 so that the total gain of a power amplifier 1 has a desired gain. Since the drive amount of the drive stage amplifier 12 is optimized, damage on a final stage amplifier 13 due to overdrive can be prevented and efficiency can be improved. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
