An 8 W GaAs Class-AB amplifier for operation in envelope tracking systems

In this paper an 8 W GaAs HEMT power amplifier for operation in envelope tracking systems is presented. The application targeted is UMTS downlink operation with a peak-to-average ratio of about 7 dB. By varying the drain bias voltage between 5 V and 12 V the compression point can be shifted in the required area. Power-added efficiency is more than 45 % in this area and above 52% in the area of average output power of a UMTS signal. Gain can be kept above 14 dB in this operation mode with a variation of 3 dB.