| 摘要 |
PROBLEM TO BE SOLVED: To provide a power amplifier whose efficiency is high and whose distortion is low capable of performing distortion adjustment using a simple constitution, without having to change a gain and radio communication equipment using the power amplifier. SOLUTION: One edge of a variable impedance element 2, whose impedance is changing according to an input power level, is connected to the base of a bi-polar transistor 102 for signal amplification of the poststage. An adjustment circuit 21 (a resistance 4 and a capacitor 5) is connected between the other edge of the variable impedance element 2 and a ground. Moreover, a DC- adjusting element 22 (resistance 3) is connected between the other edge of the variable impedance element 2 and a power supply voltage terminal 1. The prestage is operated in an A class or an AB class close to the A class, and the poststage is operated in a B class or the AB class close to the B class, and the distortion characteristics of the poststage are adjusted by the variable impedance element 2, the capacitor 5, and resistances 3 and 4, so that the distortion of the prestage can be offset. Thus, the distortion characteristics of the whole power amplifier can be optimized. |
