SiGe-heterojunction bipolar transistors (HBTs) still sustain their leading RF-application position due to their good noise and HF properties. They also offer a relatively high operating voltage, which is limited by BVCEO, the emitter collector breakdown voltage with open base. We show that BVCER, the avalanche breakdown with a
resistor RB connected to the base, can be used to define reliable operating conditions exceeding BVCEO. The measured BVCER data correlate very well with values calculated from basic transistor parameters and their corresponding multiplication factor data. The functionality of this concept is verified by investigating a power amplifier circuit used at emitter collector voltages exceeding BVCEO in operational mode enabling significant higher output power.