What is thermal run away in bipolar transistors?

Answer 1

A "thermal runaway" occurs when a transistor is heated to such a point, that the more heat it has, the quicker it will accumulate it. This usually involves leakage current which typically increases with temperature, and which causes more current to flow - which increases the heat buildup in the transistor more, and the cycle continues. This heat buildup rapidly accelerates, and it invariably and quickly (in a matter of seconds or quicker) burns out the transistor as it reaches temperatures it was not meant to safely handle.

Answer 2

Thermal runaway in bipolar transistors occurs when the transistor's temperature rises uncontrollably due to excessive current flow, leading to a feedback loop where increased temperature further increases current flow. This can damage the transistor and surrounding components, ultimately causing the transistor to fail. Thermal management techniques such as heat sinking and current limiting are used to prevent thermal runaway.