Development of a GaN HEMT class-AB power amplifier for an envelope tracking system at 2.45 GHz

A class-AB power amplifier was designed for an envelope tracking (ET) application. Class-AB amplifier is widely used in wireless communication systems due to the compromise between linearity and efficiency. As a power device, Cree Gallium Nitride High Electron Mobility Transistor (GaN HEMT) CGH4010F was chosen. The input and output matching networks were designed and simulated with Advanced Design System (ADS). After some optimization, the amplifier was fabricated using a Rogers RT/Duroid 5880 substrate. The amplifier together with a MAX2247 preamplifier as a driver was measured. A good agreement between the simulation and measurement results was observed. The maximum power added efficiency (PAE) is around 50 percents with the supply voltage V_sup= 10 V and the maximum drain efficiency is around 75 percents with V_sup= 5 V. An output power up to 42 dBm and good linearity of the output voltage with respect to the supply voltage in the range 0<;V_sup<;20V were achieved. Thus, the amplifier is suited for ET applications.