Low idle current LTE power amplifier with 2nd harmonic control

A low idle current power amplifier (PA) including an analog-predistortion bias circuit and 2^nd harmonic control circuit is presented to improve the linearity performance. For 1.85 GHz long-term evolution signals with 10- and 20-MHz bandwidths, the PA delivers a power-added efficiency of 36.1%, a gain of 31.1 dB, and an adjacent channel leakage ratio of -31.4 dBc at an average output power of 28 dBm. Even though the PA operates near a class-B mode with total quiescent current of 23mA, it achieves a good linearity for the signal with 20 MHz bandwidth. In addition, the efficiency is further enhanced to 40% by employing envelope tracking technique.