Highly Efficient Fully Integrated GaN-HEMT Doherty Power Amplifier Based on Compact Load Network

• Published in: IEEE transactions on microwave theory and techniques Vol. 65; no. 12; pp. 5203 - 5211
• Main Authors: Lee, Hwiseob, Lim, Wonseob, Bae, Jongseok, Lee, Wooseok, Kang, Hyunuk, Hwang, Keum Cheol, Lee, Kang-Yoon, Park, Cheon-Seok, Yang, Youngoo
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-12-2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplification; Amplifiers; Capacitors; Circuit design; compact load network; Doherty power amplifier (DPA); Gallium nitrides; gallium-nitride high-electron-mobility transistor (GaN-HEMT); Impedance; Inductors; Integrated circuits; Logic gates; Shunts (electrical); small cell; Transistors; π-type transmission line (TL)
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2017.2765632

This paper presents a fully integrated gallium-nitride high-electron-mobility transistor (GaN-HEMT) Doherty power amplifier (DPA) based on a compact load network for small-cell applications. The gate width of the transistor is optimized to have a load impedance of 100 Ω with a shunt inductor that can compensate for the output capacitor using a parallel resonance. A quarter-wave transmission line (TL) with a characteristic impedance of 100 Ω is realized using a high-pass π-type lumped network for the carrier amplifier. The on-chip input network, including a power splitter, a quarter-wave TL, and matching networks for the carrier and peaking amplifiers, is designed using lumped components. The circuits are simplified by merging the multiple shunt components at a node into an inductor or a capacitor. As a result, the load network has only two shunt inductors. To verify the proposed circuits, a 2.6-GHz DPA integrated circuit (IC) was designed and implemented using a 0.4-μm GaN-HEMT process. The implemented IC, which was mounted on a quad-flat no-lead package, exhibited a high drain efficiency of 54.4% at an average output power of 37.6 dBm with an adjacent channel leakage power ratio of -27.0 dBc using a downlink long-term evolution signal having a channel bandwidth of 10 MHz and a peak-to-average power ratio of 6.5 dB.