Analysis of electro-thermal instability in bipolar transistors

This paper illustrates an analytical method to determine the electro-thermal instability due to self-heating and impact ionization in terms of dissipated power and junction temperature. The analysis is carried out for single transistors (corresponding to silicon and gallium arsenide technologies) as well as for scaled devices to appreciate the use of dissipated power for determining the safe operating region of bipolar transistors. Our analysis is supported by the already reported numerical, PSPICE and experimental data from the literature and shows that at usual operating conditions the small geometry devices have less safe operating region compared to the larger ones.