New method to determine the HBT's capacitances using multi-bias S-parameter measurements

A new method to determine the base-emitter and the intrinsic and extrinsic base-collector capacitances is proposed. It uses nonlinear equations obtained from a combination of six coefficients of polynomial functions named "expression blocks". The polynomial function are derived from suitable organisation of combined Z-parameter analytical expressions of the small-signal HBT equivalent circuit. The value of each "expression blocks"" is extracted in the adequate frequency range from S-parameter measurements. The method is validated treating HBTs at multi-bias conditions.