CDIAN001: Stability Considerations When Designing Microwave Power Amplifiers

Today’s device landscape appears to be a gold mine for newly minted microwave engineers. In many ways, GaN has become the great equalizer, allowing even inexperienced engineers to build amplifiers with a level of performance that would have been unachievable 10 years ago.

The high gain, high power density, and reasonably high terminal impedances that are available with “high band gap” devices such as SiC and GaN HEMTs have provided some powerful tools to the PA designer’s “bag of tricks”, but there are still a few landmines that need to be considered early in the design process to insure a robust solution when designing a high power broadband amplifier. One that designers often step on is device stability (or more appropriately, instability). This application note will discuss the fundamental cause of this instability, and practical methods to mitigate the problem in a real world environment.
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