A wide supply voltage and low-rx noise envelope tracking supply modulator IC for LTE handset power amplifiers

A high efficiency envelope tracking supply modulator IC for LTE handset use is presented. It is fabricated using 0.35 μm CMOS with optional 6-V-MOSFETs, and operates at a wide supply voltage range from 2.9 to 6.0 V. This enables the supply modulator to be directly connected to a lithium-ion battery. The switching noise of the supply modulator is carefully designed to meet the received band (Rx) noise requirement. An envelope tracking power amplifier (ET-PA) consisting of the modulator IC and an InGaP/GaAs-heterojunction-bipolar-transistor (HBT) PA-IC is examined with 1.95-GHz-band, 10-MHz bandwidth long-term-evolution (LTE) up-link signal. Despite a use of high-breakdown-voltage CMOS process for the modulator, the ET-PA achieves a power-added efficiency (PAE) of 33.4% at an output power of 26 dBm with an adjustment channel leakage power ratio (ACLR) of -35 dBc. In comparison with a conventional PA, the PAE has improved 3.0 and 7.3% at an output power of 26 and 20 dBm, respectively. The Rx noise is -134 dBm/Hz.