A new dynamic, self-consistent electro-thermal model of power HBTsand a novel interpretation of thermal collapse loci in multi-fingerdevices

摘要

A new self-consistent dynamic electro-thermal model for power HBTsnis presented coupling a circuit-oriented electrical model fitted onnexperimental data with a full frequency domain thermal model. Thenthermal model provides the exact frequency behaviour of the devicenthermal impedance through a quasi-3D approach, rather than a simplensingle- or multi-pole rational approximation. The self-consistentnsolution is achieved, in large-signal periodic conditions, throughnharmonic balance analysis. The dynamic model enables us to discuss thenbehaviour of thermal collapse in multi-finger devices not only in DC,nbut also in AC conditions. In particular, a new interpretation isnproposed for the thermal collapse loci of such devices in terms ofnbifurcations, thus providing a simpler and more straightforwardnstability criterion with respect to those already presented in thenliterature