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I just got a bunch of LMV324IDR rail to rail op amps from ebay. I hooked one up and it seems to saturate 1.3v below the supply voltage (at 3.7v for 5v supply). There is no load at the output of the op amp (just a scope probe, 1MOhm).

This leads me to believe that the op amp might be counterfeit.

Am I right to assume so ? Is there a way to check ?

Edit: As requested a photo of the chip: op amp

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    \$\begingroup\$ You bought electronic components off eBay, rather than a real distributor. They are probably fake. \$\endgroup\$ – Matt Young Jan 7 '15 at 15:09
  • \$\begingroup\$ An LM324 is a couple pennies in China, LMV324 about 5-10x as much. \$\endgroup\$ – Spehro Pefhany Jan 7 '15 at 15:48
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    \$\begingroup\$ Note that the caveat in Michael's answer, "If you tested the part correctly...", is extremely important. For example, note that the input common-mode range is only guaranteed between 0 and +4V with a 5V supply. If you tied one of the inputs to a voltage higher than this, then all bets are off at the output. Show us your test setup. \$\endgroup\$ – Dave Tweed Jan 7 '15 at 16:02
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If you tested the part correctly to see the output saturated at 1.3 to 1.5V below the positive supply rail then that certainly does not live up to the claim for an LMV324 opamp being a rail to rail output part.

It could very well be that the parts you purchased are cheap junk LM324 opamps that were remarked as LMV324 to make them appear to be better parts. If so I'd call that a counterfeit.

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Suggest you set it up as a gain of two non-inverting amplifier to test it:

schematic

simulate this circuit – Schematic created using CircuitLab

If you are seeing it saturate at less than about V1 - 0.1V it's not a real LMV324

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  • \$\begingroup\$ I tried this, and on 3.3v supply the output saturates at 1.88v On a 5v supply the output saturates at 3.6v \$\endgroup\$ – Mike Jan 7 '15 at 19:04
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    \$\begingroup\$ You've got a counterfeit. If you can do it easily, it would be nice to see a sharp photo of the part markings for the benefit of others who may find themselves similarly inconvenienced. \$\endgroup\$ – Spehro Pefhany Jan 7 '15 at 19:30

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