Using two-dimensional time-dependent solutions of the Poisson and current-continuity equations and the Fourier transform method, we show that for wide emitters, the quasi-static model is valid if the intrinsic base resistance is properly distributed. Because the base often wraps around the emitter on four sides, a three-dimensional method to distribute the base resistance is derived. We compare measured and modeled S-parameters for an HBT with a single 6 mu m-diameter dot, and we show how to direct-extract the required intrinsic ECPs. We also distribute the transverse base resistance due to the base metal resistivity, and we show that using a lumped transverse base resistance is valid.