Direct Efficiency and Power Calculation Method and Its Application to Low Voltage High Efficiency Power Amplifier

Kazutomi MORI  Masatoshi NAKAYAMA  Yasushi ITOH  Satoshi MURAKAMI  Yasuharu NAKAJIMA  Tadashi TAKAGI  Yasuo MITSUI  

IEICE TRANSACTIONS on Electronics   Vol.E78-C   No.9   pp.1229-1236
Publication Date: 1995/09/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Ultra-High-Speed Electron Devices)
calculation method,  amplifier,  MMIC,  high efficiency,  high power,  low-voltage,  

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A direct calculation method of efficiency and power of FETs from d.c. characteristics determined by knee and breakdown voltages is proposed to make clear the requirements for knee and breakdown voltages of FETs under low-voltage operation of power amplifiers. It is shown from the calculation that the breakdown voltage has a greater effect on power and efficiency than the knee voltage and has to be three or more times of the operating voltage in order not to degrade efficiency under class-AB operation. A 3.3 V UHF-band 3-stage high efficiency and high power monolithic amplifier has been developed with the use of power FETs satisfying the requirements for knee and breakdown voltages under low-voltage operation. A power-added efficiency of 57.3% and a saturated output power of 31.8 dBm have been achieved for a drain voltage of 3.3 V in UHF-band. The direct calculation method of efficiency and power from d.c. characteristics, which can provide the required knee or breakdown voltage for a given efficiency, power, or bias conditions, is considered to be useful for developing power devices with various requirements for efficiency, power, and bias conditions.