AbstractA new method for the derivation of a FET‐equivalent circuit for large‐ and small‐signal applications is described. The model, which is valid at least up to 26.5 GHz, consists of 9 nonlinear intrinsic elements and 8 linear extrinsic elements. All circuit‐elements are determined from measured DC and scattering parameters without numerical optimization by an analytical method at any bias condition. The nonlinear elements are expressed by two‐dimensional spline functions of the third order. For nonlinear simulations, the harmonic‐balance technique, combined with a successive approximation method without function derivations is used. A modified harmonic‐balance technique is applied for nonlinear simulations o