Defining Transistor Load Impedances for Optimum, “Anti-Fragile” RF Amplifier Performance (Download)
When designing RF/microwave power amplifiers working under nonlinear operation, defining the fundamental-frequency load impedance, without ignoring the second- and third-harmonic load impedances, is critical for achieving optimal, robust, or even “anti-fragile” performance. Although numerous scholarly resources describe methods for determining these impedances for waveform-shaping modes like Class B, Class F, Class-inverse F, Class J, and their broadband derivatives, such methods often rely on complex mathematical expressions. These approaches can be challenging for engineers without advanced degrees.
This article presents straightforward procedures to define these impedances for optimal performance and robustness against tolerances, using accessible tools and nonlinear transistor models.