Methodology for accurate extrapolation of InGaP/GaAs HBT safe operating area (SOA) for variations in emitter area and ballast resistor size

The authors present a methodology for extrapolating the safe operating area for HBTs, accounting for variations in emitter area and ballast resistor size. Measurements of SOA curves for HBTs with varying emitter areas and ballast resistor sizes were made, and a simple mathematical extrapolation developed for other SOA curves. This extrapolation was successfully demonstrated as predicting a further SOA curve.