XPost: sci.electronics.design   
   From: tiwill@seventransistorlabs.com   
      
   "Kevin Aylward"  wrote in message   
   news:Pdedne3rNa5uG7bBnZ2dnUU7-aHNnZ2d@giganews.com...   
   > Well... overcurrent on a mosfet output device is usually pretty safe for   
   > quite a while. Second breakdown is the problem with bipolar. Their rating   
   > at high voltage is much lower than their power ratings would imply.   
      
   Used to be true -- modern MOSFETs are more than current-dense enough to   
   exhibit 2nd breakdown.  I shouldn't actually say modern, because apparently   
   SuperJunction process has... PTC source connections or something?  I haven't   
   seen one without a square SOA yet I don't think.  So by now, it's actually   
   previous generation that you have to watch out for.  I forget if lower   
   voltage (SJ goes away under ~400V I think it was?) processes are still   
   prone.   
      
   Tim   
      
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   Seven Transistor Labs, LLC   
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