Effect of printed circuit board structures on temperature-dependent gain characteristics of RF power amplifier chips

Jeongkyu Heo, Jae Choon Kim, Ki Hyuk Kim, Jae-Sung Rieh, Jin Taek Chung, Sung Woo Hwang

Research output: Contribution to journalArticle


We fabricated and characterized heterojunction field effect transistor radio frequency (RF) power amplifier (PA) test fixtures, for wireless applications, with various printed circuit board (PCB) structures. The RF matching and bias circuits of the test fixtures were designed so that they had the same RF characteristics. The only source of the variation of the RF gain (S21) was different thermal characteristics of each PCB. The values of the junction temperature (TJ) and the junction-to-ambient thermal resistance (RJA) of each test fixture were shown to be changed as much as 80°C and 30°C/W, respectively, by the change of PCB structures. The change of RJA was shown to be originated from the change of the PCB thermal resistance, assuring that the structure of the PCB was the dominant factor in determining RJA . Finally, we obtained a universal relation between S21 of the amplifier and TJ. This work suggests that thermal budget of PCB is as important as that of package in wireless RF equipments.

Original languageEnglish
Article number4497809
Pages (from-to)323-325
Number of pages3
JournalIEEE Microwave and Wireless Components Letters
Issue number5
Publication statusPublished - 2008 May 1



  • Power amplifier (PA)
  • Printed circuit board (PCB) thermal resistance
  • Radio frequency (RF)
  • Thermal design

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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