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Old October 30th 19, 02:58 PM posted to rec.audio.pro
Ralph Barone[_3_]
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Posts: 40
Default overvoltage on audio circuits

> wrote:
> On 29 Oct 2019 11:28:57 -0400, (Scott Dorsey) wrote:
>
>> geoff > wrote:
>>> On 29/10/2019 8:04 am, gareth magennis wrote:

>
>> And.. a lot of people would run the 5532 at +/-24V, outside the rated
>> envelope. If you tried this, a lot of them would fail in the first week,
>> but after that they all seemed to keep running fine. I gather there was
>> some variation in the thickness of the oxide layers on the chip and the
>> ones that were a little thinner got selected out..
>>
>>> But the 24V previously mentioned somewhere distinctly not good, unless I
>>> misunderstood the context.

>>
>> If it was going to fail, it probably would have failed by now. I would be
>> much more worried that the supply issues will degrade the sound quality.

>
> Electronic circuits have a mechanical wear-out mechanism caused by the momentum of the
> electrons in the current flow moving the conductor atoms slightly if they
> collide. Over time,
> enough atoms will have moved that a void will open in the conductor line,
> breaking the path
> and the circuit. This electromigration is a very
> strong exponential function of current density
> and temperature (among other things.) Circuits are designed to last ten years under speced
> conditions. So, even if you get an amp that is at the high end of the
> manufacturing distribution
> for breakdowns, running at higher voltages increases the temperature and
> exponentially reduces
> the life. Depending on wafer process and circuit package, going from 18V
> to 24V could significantly
> lower the life of the circuit by many years.
>
> This mechanism exists in all electrical conductors, but is only an issue
> in microcircuits because the
> conducting lines are so small and the current densities are therefore very high.
>


I was under the impression that electromigration was only an issue in
modern microprocessors and other ICs built using nanometer scale
transistors. I would assume that an op amp is built with huge transistors
(and huge traces) in order to achieve low noise, and would therefore be
relatively immune to electromigration damage.

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