[sdiy] low input bias current opamps

ASSI Stromeko at nexgo.de
Wed Aug 15 22:01:48 CEST 2018


On Wednesday, August 15, 2018 7:37:24 PM CEST David G Dixon wrote:
> Possibly stupid follow-up question:
> 
> Why would ESD have an effect on a JFET-input opamp?  I thought that only
> CMOS was susceptible to ESD, because of the oxide gate insulator, but not
> JFET.  The LF444 should be no more susceptible to handling issues than
> TL074.  The handling would have to have been unbelievably abusive to damage
> the chips, I would have thought.

When a lightning strikes you, that's just an ESD event, so saying only CMOS is 
susceptible for ESD is obviously wrong.

The only reason you don't hear as often about ESD damage of junction 
transistors is that an ESD pulse gets to dissipate its energy across a larger 
volume of material, which makes it less likely to create catastrophic damage.  
Given enough energy it will melt some of the silicon however, and the part 
will cease to work as intended after that.  Excessive leakage is just the 
first sign of such damage and much more noise than usual another.  It quickly 
goes downhill after that.

About the original trigger for your question: How sure are you that these 
actually were pristine and genuine LF444?  While assembly lines with ESD 
problems can be surprisingly repeatable in the type and amount of ESD damage 
that gets produced, it is highly unusual that the whole run would suffer 
exactly the same fail.


Regards,
Achim.
-- 
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SD adaptations for Waldorf Q V3.00R3 and Q+ V3.54R2:
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