27.5 A 91%-Efficiency Envelope-Tracking Modulator Using Hysteresis-Controlled Three-Level Switching Regulator and Slew-Rate-Enhanced Linear Amplifier for LTE-80MHz Applications

Envelope tracking (ET) is widely used to improve the efficiency of linear power amplifiers (PAs) in applications such as LTE, LTE-Advanced inter- or intra-band carrier aggregation (CA), and for high-speed uplink packet access (HSUPA) with a high peak-to-average power ratio (PAPR). The hybrid ET modulator (ETM), where an efficient switching regulator (SWR) operates in parallel with a fast class-AB linear amplifier (LA), is one method to address the bandwidth (BW), power-efficiency and output ripple requirements.