1. Bipolar power transistors

For a long time, transistors were the only semiconductor elements that enabled power switching between on and off states without any prior polarity change. Due to the complexity of their control and their relative fragility, MOS transistors, IGBTs or GTO thyristors are preferred today, depending on the current and voltage range. However, because of their low cost, they are still used in a number of mass-market applications (electronic ballasts, for example). Although the industrial importance of bipolar power transistors is declining, the study of this component is essential: because of the physics of its operation, it represents an archetype, with the mechanisms it brings into play also playing a part in the normal or faulty behavior of most other components.