A High Efficiency and High Linearity GaAs HBT Doherty Power Amplifier for 5G NR 3.4V Application

This work presents a 3.3-4.2 GHz broadband twostage fully differential Doherty power amplifier (DPA) for 5G new radio (NR) handset applications with low supply voltage 3.4V. It is implemented by 2-mu m GaAs HBT Flip-chip process for PA and 6-layer laminate substrate process for output transformer and matching networks. To cancel the non-linearity components of carrier amplifier and peaking amplifier, bias currents of driver amplifiers were optimized to adjust different input power level for carrier and peaking power cell. In addition, equivalent multi-segment low-pass networks of./4 transmission lines were designed to expand the bandwidth of impedance transform in DPA. For continuous-wave (CW) signal, the implemented DPA module exhibited a saturation power of 33.4 to 34.8 dBm, and PAE of 38 to 43% in full N77 band. Using the 5G new radio 100-MHz QPSK signal, this work shows high linear power of 31 dBm with 34% PAE and 30 dBm with 31% PAE at N78 and N77 band, respectively. The corresponding adjacent channel leakage ratios (ACLRs) are lower than -36.5dBc without digital pre-distortion (DPD).