Energy-Based Capacitance Modeling for Field-Effect Transistor Stability Analysis

Certain industry-standard transistor models exhibit nonreciprocity of capacitances in the subthreshold mode. This behavior violates the law of energy conservation and impedes stability analysis of MMIC circuits, especially class C amplifiers. We circumvented this limitation by introducing a new modeling approach: energy-based capacitance modeling. Instead of modeling capacitances or charges, we model the electrical energy stored in the transistor. From this quantity we derive expressions for charges and capacitances by means of differentiation. We applied this approach to an LDMOS device and achieved very good accuracy, while maintaining charge and energy conservation.