Patent ID: 8093948

Claim:
A power amplifier comprising: an amplification section amplifying an input signal according to an adjustable gain to thereby output the amplified input signal; a detection section detecting signal levels of an input signal and an output signal of the amplification section; and a gain maintaining section controlling a bias power according to a detection result of the detection section so that a gain of the amplification section is maintained within a predetermined gain range, wherein the gain maintaining section comprises: a gain calculations unit calculating the gain of the amplification section according to the detection result of the detection section; a comparison unit performing a comparison to determine whether a calculation results of the gain calculation unit is within the predetermined gain range; and a bias supply unit supplying a corresponding bias power according to a result of the comparison of the comparison unit, wherein the comparison unit comprises: a first comparator having a positive (+) terminal receiving the calculation result of the gain calculation unit and a negative (−) terminal receiving a first-range voltage having a predetermined voltage level; and a second comparator having a negative (−) terminal receiving the calculation result of the gain calculation unit and a positive (+) terminal receiving a second-range voltage having a predetermined voltage level lower than the predetermined voltage level of the first-range voltage.