Stability analysis and stabilization of power amplifiers

The objective of this article is to provide explanations for some of the anomalous phenomena commonly observed in the measurement of PAs. It will also show how modern stability-analysis techniques, based on harmonic balance, can accurately predict the undesired behavior. The article introduces practical simulation tools, applicable on both in-house and commercial harmonic balance simulators. The identification of the mechanisms behind the different instability phenomena will lead to an efficient derivation of accurate techniques for their elimination from the amplifier response. For illustration, the simulation tools will be applied to a Class E/F amplifier, which showed oscillations, hysteresis, and chaos (Jeon et al., 2005). Using these tools, the amplifier will be globally stabilized for all the expected operating values of the bias voltage and input power. This will be achieved with negligible degradation of the amplifier performance in terms of output power and drain efficiency