"So, off you go to the local parts shop to buy some transistors (or indeed, other parts!). Having decided the devices that fit your needs (having selected any of a number of devices that are suitably rugged and powerful), you hand over a not insubstantial amount of cash and head home to build the masterpiece. Inexplicably, the expensive output transistors fail, but you know that their ratings are well within the design limits for the project you are building. This happens once, maybe twice, or perhaps more. You get discouraged, and shelve the project -having already spent quite a lot on all the parts needed."
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