Impact of bias schemes on Doherty power amplifiers

This paper investigates the performance of a 2.4GHz CMOS two-way Doherty power amplifier with the different bias schemes for the auxiliary power device. For the conventional bias schemes, there are design tradeoffs in terms of power gain, gain flatness, P_1dB, power-added efficiency, and third order harmonics. An adaptive bias scheme is proposed to bias the auxiliary device at class C for low power operation and at class AB for high power operation. It is shown that the adaptive bias scheme can achieve excellent performance without compromising some characteristics.