A Simple Method to Estimate the Output Power and Efficiency Load–Pull Contours of Class-B Power Amplifiers

This paper describes a simple method to estimate the output power and efficiency load-pull contours of a class-B power amplifier (PA). Using successively improved-but still simple and intuitive-field-effect transistor nonlinear i_DS (v_GS,v_DS) current models, this work starts by explaining the poor efficiency predictions provided by the Cripps load-line method, to then derive refined expressions to predict the output power load-pull contours and a novel analysis that produces useful estimates of the efficiency load-pull contours. These estimates are believed to constitute an invaluable tool for the analysis and design of single-ended class-B or Doherty PAs.