In this paper the small-signal equivalent circuit model of SiGe:C heterojunction bipolar transistors (HBTs) has directly been extracted from S-parameter data. Circuit simulations by the use of neural network architecture and a standard IHP 0.13um BiCMOS technology confirmed our design goals. To check the capability of the direct approach, scattering parameters were generated and compared with Artificial Neural Network (ANN). Then measured and model-calculated data have represented an excellent agreement with less than 0.166% discrepancy in the frequency range of > 300GHz over a wide range of bias points.