Derating is the practice of using an electronic device in a narrower environmental and operating envelope than its manufacturer designated limits. The purpose is to lower the stress (i.e., electrical, thermal, and mechanical) acting on device, in order to extend its useful operating life and to provide a safer operating condition by furnishing a "margin of safety." The term "derating" by definition suggests a two step process; first a "rated" stress value is determined from a device manufacturer's databook and then some reduced value is assigned. The tendency for the system design team leans towards using conservative stresses at the cost of productivity.

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