Compact Large-Signal Shot-Noise Model for HBTs

A new description of the shot noise in HBTs is proposed that accounts for the correlation of the sources. It can easily be included in large-signal models, thus significantly improving the RF noise description. Common nonlinear bipolar transistor models thus far neglect the correlation, which deteriorates the model accuracy towards higher frequencies. It is shown that the collector delay in InGaP/GaAs HBTs dominates the shot noise correlation. Hence, the collector time-delay description of the large-signal model is capable of providing suitable noise correlation time constants. The model is verified against measurements of InGaP/GaAs HBTs with three different epitaxial layer designs.