A Broadband Doherty Amplifier With Back-Off Efficiency Enhancement

In this letter, a technique by distributing more power to the main amplifier of the Doherty amplifier is proposed to improve the overall efficiency of the back-off region for the first time. A mathematical model is established to qualitatively verify the efficiency enhancement of the back-off region. The quasi-lumped transmission line is used for circuit implementation, and analytical formula for the design is deduced, which reduces the time and difficulty of Doherty output matching design. The circuit measurement results prove that 44.3% fractional bandwidth is achieved, while drain efficiency within the frequency range at 6 dB back-off is greater than 59% with peak power output 46.5 dBm.