Enhanced empirical large-signal model for HBTs with performance comparable with physics-based models

Abstract

An accurate empirical large-signal model for an heterojunction bipolar transistor (HBT) is given. In the DC mode, thermal-dependent physics-based relations for Kirk and avalanche effects are included to improve the accuracy of the model. In the small-signal mode, in addition to the distribution of the base resistance and base collector junction, the model captures the variation of various AC parameters with both bias voltage and bias current over the entire forward-bias region and a wide range of signal frequencies. DC parameter extraction is easily carried out using suitable optimisation codes on the measured I/sub c/-V/sub ce/ curves and Gummel plots, whereas the AC parameters are determined from multibias S-parameter measurements. To assess the validity and the accuracy of the proposed model the empirical large-signal model is constructed for a 2/spl times/25 /spl mu/m/sup 2/ emitter-area transistor and compared with measurements in DC, small-signal and large-signal modes. The model is further tested by comparing it with the physics-based and well-established VBIC model. It is found that, despite its reduced complexity, the enhanced empirical model gives better agreement with measurements than the VBIC model in all modes of operation.