A CMOS envelope tracking power amplifier for 4G LTE mobile terminal applications

An envelope tracking power amplifier (ET PA) using a standard CMOS process for the 3GPP long-term evolution mobile terminals is presented. An efficiency of the CMOS power amplifier for the modulated signals can be improved combining with a highly efficient and wideband CMOS bias modulator. The CMOS PA has a two-stage differential common-source structure for high gain and large voltage swing. The bias modulator has a hybrid structure which consists of a linear stage and a switching stage. The variable load condition according to the envelope signal level is taken into account for the bias modulator design. By applying the bias modulator to the power amplifier, the ET PA delivers a PAE of 41.7 % at an average output power of 24 dBm, which is 5.3 % points higher than that of the power amplifier alone at the same average output power and linearity.