Absolute maximum ranges for ic's

Some op amps and other devices say they have an absolutely maximum voltage range of 40V(+- 20V). If I were to run these off 4 9.6V batteries in series or 3 12V batteries in series will it be a bad idea since it may exceed the spec? Can these devices generally run a bit higher without harm? 40V is just right around the standard 3*12 or

4*9.6 except that the maximum voltage of these may actually end up exceeding the 40V by a few volts.

Is "absolute maximum" something we shouldn't get close to or something we can design up to and even go over slightly(10% maybe) without worrying too much more about the device failing?

Reply to
Juo
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Old linear processes, like LM741s, were usually very tolerant of being run at or a bit above abs max. Somebody told me that LM741s work at 60 volts. I've used some superfast modern opamps that died just a tiny bit above abs, so I wouldn't use them anywhere close.

Without more info or testing actual parts to limits, I wouldn't push past abs max. Lots of guys would never run parts above, say, 80% of abs max.

John

Reply to
John Larkin

I'd even go a step further, and use the numbers in the "operations" section of the data sheet, where they tell you the test specs, then I'd use the test specs as the max.

Cheers! Rich

Reply to
Rich Grise

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If the absolute maximum is 40 volts, then 4 * 9.6 = 38.4V and 3 * 12 =
36V, which won't exceed the spec.
Reply to
John Fields

I used the LM343 once, right on its 40V maximum rating. We started off powering it with a lab power supply, and it blew up regularly, but once I'd put together my carefully toleranced 39+/-1V power supply we never lost another.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

three leadacid 12V batteries just charged it'll be, 3 * ~13.2 = 39.6 that's cutting it close if they are charging it will more like ~42V

-Lasse

Reply to
langwadt

--
Your point?
Reply to
John Fields

Let 'em find out on their own what ABSOLUTE means ;-) ...Jim Thompson

--
                  [On the Road, in New York]

| James E.Thompson, CTO                            |    mens     |
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Reply to
Jim Thompson

you said three 12V batteries won't exceed the spec of a 40V part, in practice it is very likely to see over 40V

-Lasse

Reply to
langwadt

you said three 12V batteries won't exceed the spec of a 40V part, in practice it is very likely to see over 40V

-Lasse

-------------- Don't worry about him... he doesn?t have a clue.

Not all 9V batteries are 9V or even 9.6V. Some lithium varieties can even go high as 11V. If the OP circuit will run off a wall-wart then the max voltage is always higher than the nominal voltage. Not that 36V wall-warts are common but I've seen a few... with 42V unloaded.

Reply to
DonMack

e

If you do, failures are likely. But for one offs, with some parts one can exceed ratings by a huge margin and have the result works fine for decades. And sometimes it really is abs max. So 'dont ever' just cant be assumed. Some parts ratings can even be exceeded for production runs on occasion, especially for novelty or seasonal products. Some parts are more tolerant than others.

I once exceeded power ratings hugely with silicon, adding a heatsink to a part not intended for it. It worked fine, repeatedly. The chip's thermal performance junction to case wasnt specced, nor was the heatsink, which was just a bit of sheet metal. Costs needed to be cut hard. They ran 20% above abs max V, at a few times rated Pdiss, and there were no failures. However... you takes your chances. Some parts just wont tolerate it, and you can easily wind up wasting time.

Mains transformers are candidates for respeccing too. Heatsink them with aluminium snippings and they can be pushed. But as always, the reliability must match the market.

NT

Reply to
NT

Do you know how to READ????? "Absolute maximum" MEANS exactly what it states;; it is !NOT! to be used for running designs.

Reply to
Robert Baer

Wise!

Reply to
Robert Baer

Quite right, Robert, I mean, you'd never exceed the maximum temperature spec, would you? ;-)

Cheers

--
Syd
Reply to
Syd Rumpo

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The maximum voltage out of a wall-wart is _always_ higher than the
nominal?
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Reply to
John Fields

Reliability data typically show failure rates climbing rapidly from below the absolute max limits. If the device is to be reliable, you need to be "well below" those limits. How many seconds does this device have to live?

Reply to
cassiope

ven go=20

oltage=20

=20

Reply to
m II

"Absolute Maximum" means what it says; Operation outside the specified ratings may cause the device to malfunction, or fail. The manufacturer takes no responsibility for operation outside the published ratings.

Whilst you might get one specimen to operate satisfactorily outside ratings, another from a different manufacturer, or even a different batch from the same manufacturer might not.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
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Reply to
Fred Abse

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