A High-Efficiency Low-Distortion Cascode Power Amplifier Consisting of Independently Biased InGaP/GaAs HBTs

Yuki TAKAGI
Yoichiro TAKAYAMA
Ryo ISHIKAWA
Kazuhiko HONJO

Publication
IEICE TRANSACTIONS on Electronics   Vol.E97-C    No.1    pp.58-64
Publication Date: 2014/01/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E97.C.58
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
Keyword: 
cascode,  InGaP/GaAs HBT,  microwave power amplifier,  

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Summary: 
A microwave power amplifier with independently biased InGaP/GaAs HBTs is proposed, and its superior performance is confirmed. Using harmonic balance simulation, the optimal bias conditions for an amplifier with two independently biased InGaP/GaAs HBTs were investigated with the aim of achieving high-efficiency low-distortion performance. A 1.9-GHz-band cascode power amplifier was designed and fabricated. Power efficiencies and third-order intermodulation distortions (IMD3) for the fabricated amplifier were estimated. The collector bias voltage of the first stage transistor mainly affects power-added efficiency (PAE). The base bias current of the first-stage HBT mainly affects IMD3 characteristics, and that of the second-stage HBT mainly affects PAE. The proposed amplifier shows superior performance when compared to a conventional cascode amplifier. The amplifier achieved a maximum PAE of 68.0% with an output power of 14.8dBm, and IMD3 better than -35dBc with a PAE of 25.1%, for a maximum output power of 10.25dBm at 1.9GHz. A PAE of more than 60% was achieved from 1.87 to 1.98GHz.