Efficiency determination of RF linear power amplifiers by steady-state temperature monitoring using built-in sensors

This work aims at showing a new approach for determining the efficiency of linear class A RF power amplifiers by means of non-invasive, steady-state thermal monitoring. The theoretical basis of the technique is indicated and its suitability in a real case application scenario is presented. More in detail, silicon surface thermal monitoring is performed with built-in sensors and infrared measurements on an RF power amplifier. The first monitoring circuit consists of differential sensors, which can be used for contact-less on-line efficiency monitoring or to easy production testing. The obtained results are corroborated by means of Infrared measurements. Off-chip temperature sensors have applications in failure analysis or circuit debugging scenarios. As a result, we observe a good agreement between the efficiency predicted with the thermal measurements (less than 5% of error) when compared to values measured with standard electrical equipment.