Design and implementation of high power amplifier using gallium nitride

Abstract

In recent years, the use of Gallium Nitride (GaN) transistors as active device inpower amplifier circuits has increased. The advancement in the technology forsuitable substrate has allowed the use of this very promising material. In this thesis,a Radio Frequency (RF) power amplifier is designed using GaN HEMT fromCree, 4600 Silicon Drive, Durham, North Carolina 27703, USA. The work presentsdetailed theory of amplifier including design and simulation of single and multistageamplifiers with different matching circuits. The design was implementedwith the help of large signal model from Cree. Amplifier presented here is observedto be stable over a frequency range of approximately 400 MHz (2.2GHzto 2.6GHz). Also the harmonics pose problems with power amplifiers. The harmonicscause wastage of power. The second and the third harmonics are givendue consideration because high order harmonics are not so prominent. Also, dueto the harmonic currents, the device gets overheated, and for a power amplifierthe current values would be high enough to pose serious heating problems. Herethe constraints were laid upon 2nd and 3rd harmonics (provided by SAC ISRO),and the simulation results are observed to be in accordance. The output powerachieved is 31.23 dBm (at input power 10 dBm) which shows the gain to be around21 dB even at such high input power level.