A new methodology for the extraction of nonlinear models for microwave transistors is proposed. A unique nonlinear equation for Ids in conjunction with a N-terminal high order filter provides good results in the modeling of gm and gds behavior in high, medium and low frequencies. Emphasis in the KHz range is shown in order to study memory effects and frequency dispersion. Results of measurements reveal the accuracy of this model under small and large signal conditions, for different kind of devices. The methodology used in this work can be incorporated into other Ids models to improve its capabilities using only one current source in a new large signal equivalent circuit. © 2014 IEEE.