EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: prosper on October 13, 2022, 07:11:14 pm
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I bought a strip of 'LMV358's from China. Naturally, there was always a good probability that they'd be fake, given that they were like $0.08 each.
I hooked one up to a function generator and a scope, and to my surprise, they actually act like 'real' LMV358's.
Now, I'm quite sure they're fake for two reasons:
1. The 'TI' markings wipe right off
2. It performs better than the TI datasheet indicates. TI lists the common-mode input range as spanning up to about 0.6V below Vdd, and these guys happily go right up to the rail.
Other specs, like slew rate, output range, offset, etc - are all in the right ballpark or a bit better than 'typical' values. I know there are differences in LMV358's - e.g. ST and ONsemi datasheets claim that their products are rail-to-rail input and output (unlike TI). So, did I just get a 'rebadged' Chinese generic LMV358? Or do genuine TI parts actually work better than advertised?
Are there any other fakes that you've found that are actually kinda.... good?
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I once encountered counterfeit Coilcraft RF transformers that electrically worked better than the originals by not having a parasitic resonance at a certain frequency. But the physical construction was considerably worse. I think that was just by chance.
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Yeah, I'm thinking I just got lucky. Who knows what I'd get and how another order would perform. However, I'm happy to have a good supply of really useful opamps in my stash.... But i certainly wouldn't design an actual product with these, with the uncertainty around what they actually ARE, and whether I could get more like them
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The problem with counterfeits is you don't always know which corners have been cut. For example, the LM2956 modules that are ubiquitous oscillate at the wrong frequency and have no thermal or overload protection. So do they work when you use them as the average punter would? Sure! But it doesn't mean the counterfeit is any good.
I would expect that genuine chips work better than the datasheet suggests. The datasheet is a guaranteed minimum performance level.
OTOH, if your design requires the chips to work better than the datasheet suggests (and based on your limited testing of a few specific samples) you are setting yourself up for failure.