3.4 A dual-mode transformer-based doherty LTE power amplifier in 40nm CMOS

Modern high-data-rate communication systems such as LTE use spectrally efficient modulation schemes with a high peak-to-average power ratio (PAPR), placing stringent linearity demands on the RF power amplifiers (PA). The main challenge for LTE power amplifiers is therefore to achieve high efficiency and high linearity for a wide power range. In addition, delivering Watt-level output power is another challenge for CMOS RF power amplifiers due to the low breakdown voltage of the transistors. Series-combining transformers (SCT) enable high output power levels by summing up the output voltages of low-voltage CMOS power amplifiers [1-4].