Characterization of RF power BJT and improvement of thermal stability with nonlinear base ballasting

A novel base ballasting scheme for interdigitated power RF bipolar transistors has demonstrated improved performance and thermal stability. The nonlinear ballast resistor in series with each base finger is implemented using a depletion-mode FET, which requires only minor modification in the fabrication process. Mixed-mode simulation, instead of analytical equations, is used for more accurate device characterization.