Dual-mode supply modulator for CMOS envelope tracking power amplifier integrated circuit

A dual-mode supply modulator is presented for a complementary metal-oxide semiconductor envelope tracking power amplifier (PA) integrated circuit. The proposed supply modulator, based on a hybrid buck converter, has dual Class-AB buffers and dual switches for the linear and switching amplifiers, respectively. For high average output power levels [or high-power mode (HPM)], the supply modulator is controlled to have full sizes for both the buffer and switch to supply peak envelope voltage and high output current to the PA. The supply modulator is reconfigured to have smaller sized Class-AB buffer and switch for low average output power levels (or low-power mode). The smaller sized buffer and switch are used to reduce the quiescent current of the linear amplifier and to maintain high efficiency of the switching amplifier for a lightly loaded condition. For the 16-QAM LTE uplink signal with a channel bandwidth of 5 MHz, the PA with the proposed supply modulator delivered a power-added efficiency of 46.2% at an average output power of 24 dBm for a high power mode, which shows an improvement of 8.0% compared to the stand-alone PA. For a low power mode, the PA with a reconfigured supply modulator has a power-added efficiency of 12% at an output power of 9 dBm, which is a back-off of 15 dB. This is 1.6 and 7.2% higher than that using the supply modulator for the HPM and for the stand-alone PA at the same output power, respectively.