Control of saturation of integrated bipolar transistors

摘要

Saturation of a bipolar power transistor is controlled by sensing the current which is eventually injected into the substrate of the integrated circuit by the saturating transistor and using this signal for exerting a limiting action on the current which is driven to the base of the power transistor by a dedicated driving circuit. Unlike the prior art antisaturation systems, it is no longer necessary to precisely monitor the operating voltages across the terminals of the bipolar power transistor. A suitable sensing resistance may be integrated conveniently at a distance from the often complex integrated structure of the bipolar transistor. The system of the invention offers numerous advantages and ensures intervention of the antisaturation circuit only when the power transistor has positively reached a state of saturation, but well before any unwanted consequence.