A Wideband CMOS/GaAs HBT Envelope Tracking Power Amplifier for 4G LTE Mobile Terminal Applications

A high-efficiency envelope tracking power amplifier for long-term evolution (LTE) handset mobile terminals is presented. The envelope amplifier consists of a wideband buffered linear amplifier as a voltage source and a hysteretically controlled switching amplifier as a dependent current source. The linear amplifier has a high current drive capability of approximately 500 mA while consuming only 12 mA of quiescent current. The impact of envelope shaping on system efficiency and stability is investigated. The envelope amplifier is implemented in a 0.15-mu m CMOS process and tested with a GaAs HBT RF power amplifier. For a 20-MHz LTE signal with 6.6-dB peak-to-average power ratio, an overall efficiency of 43% is achieved at 29-dBm RF output power level with relative constellation error below 1.9% after digital pre-distortion.