Comparative study of shot-noise models for HBTs

Although the shot-noise sources in bipolar transistors are strongly correlated, it is highly desirable for several reasons to rely on an approximative model that requires only noncorrelated sources. The two common topologies employing either two noncorrelated noise-current sources, or a noise-voltage and a noise-current source, are analytically analyzed and experimentally compared for the example of a GalnP/GaAs HBT. Differences and limitations of the two models are discussed, and it is shown how the topology can be modified in order to formulate a model based on noncorrelated sources that is accurate up to the transit frequency.