[time-nuts] Simulation

jimlux jimlux at earthlink.net
Mon Aug 16 00:16:18 UTC 2010


J. Forster wrote:
> It depends on whether the leakage continues to rise or stabilizes after a
> "burn in" period.
> 
> -John
> 
> ============
> 
> 
>> Hi Bob yes that was a point raised by Prof Nat Sokal after I published
>> some
>> data, or rather he pointed out it happened in RF amps. I guess if you take
>> an used PA transistor out of service and measure it you might find the
>> base
>> emitter junction very leaky, but does  few mA of leakage matter so much in
>> a
>> low impedance high drive power circuit.
>> Reliability asks "does it do the job it was designed for" not "is it as
>> good
>> as new now"
>>
>> Alan
>
We get into the argument about "still works ok in the circuit" vs 
"doesn't meet databook specs" all the time at work.  To some folks, "not 
meet datasheet" = "failure", while if you have a circuit that needs a 
gain of 10, and the part has a gain of 1000, and degrades to 500, it's 
hardly failed.

And rarely, do you have the budget or time to do a real "life test" to 
prove it experimentally.


In radiation environments, it's more of a continuous aging effect.. more 
  dose, more leakage.  And what drives the conflict between designer and 
reliability guys is that the effect isn't particularly predictable, 
particularly between lots (because it's not something controlled in the 
process)

(which makes life testing all that much more fun)



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