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applying power to positive rail before the negative one or viceversa

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ricko_uk:
Thank you all! :)

ricko_uk:
If you have a prototype board with dual rail supply and have only single supply bench PSU, what's the best solution to have dual supplies which also turn on together?

magic:
If there are equal capacitances between each rail and ground, simply applying power between the rails will set the ground in the middle due to capacitive divider action.
To keep it there permanently, use a resistive divider or active rail splitter, depending on how much current imbalance is expected between the rails and supply impedance requirements.

CatalinaWOW:
AFAIK there is no universal answer for this.  You must check the data sheets.  If you don't have access to the sheets negative first is a good guess.

Many parts are designed to be insensitive to brief reversals of supply voltages, but many others will latch up and a sizable number will fry.  The only solution is to repeat - check the data sheets and conform with the requirements.

exe:
An opamp doesn't know anything about power rails, it is actually supplied by a single voltage applied between Vss and Vcc. Split rails are only used to bring input levels or output levels within required range (e.g., common-mode input doesn't include ground, or output cannot swing all the way to the ground).

So, applying only one rail... what does this actually mean? Does it mean the other rail at ground potential? If so, I'd apply a positive rail first, keeping in mind that either input will not work, or output will get above ground.

If there is no path to ground (unlikely) then the power sequence doesn't matter, as it is equivalent of no power.

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