An accurate and broad-band method for heterojuction bipolar transistors(HBT) small-signal model parameters is presented in this paper.This method differs from previous ones by extracting the equivalent-circuit parameters without using spec ial test structure or global numerical optimization techniques.The main advantag e of this method is that a unique and physically meaningful set of intrinsic par ameters is extracted from impedance and admittance representation of the measure d S-parameters in the frequency range of 0.5—12GHz under different bias conditi ons.An equivalent circuit for the HBT under a forward-bias condition is proposed for extraction of access resistance and parasitic inductance.The method yields a deviation of less then 5% between measured and modeled S-parameters.