Simulation of DC Safe Operating Area and RF Breakdown in SiGe PA HBT

This paper presents the simulation of DC safe operating area (SOA) and RF breakdown voltage in silicon germanium (SiGe) heterojunction bipolar transistors (HBT). High power HBTs engineered for advanced communications standards like 801.11ac and 801.11ax operate close to the SOA limit. DC and RF breakdown or ruggedness are therefore important considerations for power amplifier (PA) device and should be well characterized and simulated. It is shown that RF breakdown is directly correlated to DC SOA when both are measured under the base voltage bias mode. By modeling DC SOA well, RF breakdown voltage can be predicted with good accuracy. This is achieved by leveraging the improved strong avalanche breakdown current modeling at high injection levels in the HICUM/L2 v3.0 that is absent in v2.3x. The ability to accurately simulate DC SOA and RF breakdown are key features of a power amplifier model and allows the circuit designer to design for maximum output power and satisfy ruggedness criteria.