The Impact of Electro-Thermal Coupling on HBT Power Amplifiers

Thermal issues pose significant challenges for today's RF power amplifier designs. Recently, layout-based electro-thermal simulation tools have become widely available across the industry. While these tools are most commonly used for device-level reliability and lifetime verification, electro-thermal simulation can also enable engineers to gain new insight into the performance effects that are brought on by cross-circuit thermal coupling in RF power amplifiers. This paper describes the use of electro-thermal simulation to understand, predict, and account for cross-circuit thermal coupling in a commercial HBT power amplifier. Specifically, electro-thermal analysis is used to analyze how thermal coupling impacts gain compression and low frequency memory effects.