In this paper, the power amplifier using active bias circuits for LDMOS(Lateral Diffused Metal Oxide Semiconductor) MRF-21060 is designed and fabricated. According to change the temperature, the gate voltage of LDMOS is controlled by the fabricated active bias circuits, which is made of PNP transistor to suppress drain current. The driving amplifier using AH1 and parallel power amplifier AH11 is made to drive the LDMOS MRF-21060 power amplifier.
The variation of current consumption in the fabricated 5 Watt power amplifier has an excellent characteristics of less than 0.1 A, whereas passive biasing circuit dissipate more than 0.5 A. The implemented power amplifier has the gain over 12 dB, the gain flatness of less than ±0.09 dB and input and output return loss of less than -19 dB over the frequency range 2.11 ~ 2.17 GHz. The DC operation point of this power amplifier at temperature variation from 0 ℃ to 60 ℃ is fixed by active bias circuit.