Highly Efficient Saturated Power Amplifier

In this article, a high-efficiency saturated amplifier has been presented. This amplifier takes advantage of the nonlinear output capacitor to shape the voltage waveform. The nonlinear capacitor generates substantial second harmonic voltage with small higher order harmonics. Thus, using √2 times larger fundamental load and the proper second harmonic termination, the resultant voltage waveform can be half-sinusoidal. For high efficiency, the PA should be driven by the large input power. Therefore, the current of the PA is bifurcated, resulting in the quasirectangular current shape. The resultant output waveforms are similar to those of class-F¹ amplifiers, whose waveforms are optimal for high efficiencies. Based on harmonic source/ load-pull simulation, the saturated amplifier has been designed using Cree´s GaN HEMT CGH40006P packaged model. The matching networks for the input and output were optimized using the Momentum simulator. The implemented amplifier delivered a PAE of 80.1% at 3.475 GHz. The simulation and measurement results verify that the saturated amplifier is suitable for a high-efficiency PA over a relatively high frequency band.