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Ralph Barone[_3_] Ralph Barone[_3_] is offline
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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.