Envelope-tracking two-stage power amplifiers

A two-stage power amplifier (PA) and a supply modulator are designed and implemented for envelope-tracking (ET) operation to reduce dc power consumption. The supply modulator is connected to each stage of the PA and further enhances efficiency in a back-off power region. The envelope of a signal is reshaped to achieve good linearity and efficiency. The ET PA performs a power-added efficiency (PAE) of 39.6% (5% higher than a stand-alone PA) and an adjacent channel leakage power ratio (ACLR) of -33.8 dBc at an average power of 27 dBm and a operating frequency of 1.85 GHz with a long term evolution (LTE) signal having a peak-to-average power ratio (PAPR) of 7.5 dB, a bandwidth (BW) of 10 MHz, and a 16-quadrature amplitude modulation (QAM). The ET PA also delivers a PAE of 20.6% at an average power of 17 dBm, and the performance is 5.8% higher than the ET PA tracking only the power-stage and 9% higher than the stand-alone PA.