High efficiency amplifiers for 8 GHz band

This paper describes newly devised high efficiency amplifiers. They are single and push-pull power amplifiers operating in 8 GHz band. In the single amplifier, a trapezoidal voltage waveform is produced at a FET in the first stage of the circuit, and the operating angle is set to 74/spl deg/. This voltage is amplified in the exciting stage and the power amplification is performed by a power FET in the final stage. Using a FET whose characteristics are the same as those of the FET used in the proposed amplifier, the conventional class A and class C power amplifiers are also constructed. For the three (new and conventional) amplifiers, a comparison is made in the output power and the power added efficiency, and the predominance of a new high efficiency power amplifier is demonstrated. The operating frequency is in 8 GHz band, and the output power is 2 W, 2.35 W, and 3 W for class A and class C amplifiers, and the new amplifier, respectively. For these amplifiers, the power added efficiency is 30%, 48.5%, and 60%. A high efficiency push-pull power amplifier is also constructed, and a maximum power of 7 W and power added efficiency of 76% are obtained.