Are those genuine Analog Devices OP2177 and AD736? - Page 1
Forum section: electronics / general

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 06:36:11 pm
content: Am I under scam?

author: tom66
author_rank: Super Contributor
timestamp: May 27, 2015, 06:39:13 pm
content: AD logo is completely wrong, the logo is square and the triangle is very close to if not exactly equilateral.So I would say they are fake

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 06:50:57 pm
content: Quote from: tom66 on May 27, 2015, 06:39:13 pmIf they are fake, how can I tell how fake are these? Not gonna meet the spec fake or just not genuine but will work fine fake?

author: tom66
author_rank: Super Contributor
timestamp: May 27, 2015, 06:56:04 pm
content: Quote from: technix on May 27, 2015, 06:50:57 pmThere is absolutely no way to tell, unless you can test every characteristic of them. For all you know it could be completely nonfunctional or a remarked Chinese clone which performs identically.But, if it's anything like most fake opamps, the devices will be some similar remarked part which behaves roughly correctly but does not meet specifications.

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 06:59:08 pm
content: Quote from: tom66 on May 27, 2015, 06:56:04 pmSo the only way to check the chips are is order a few samples from ADI and compare them spec to spec?And what about the AD736 true RMS converter? Can I just safely assume that they won't work?

author: slurry
author_rank: Regular Contributor
timestamp: May 27, 2015, 07:15:25 pm
content: "computer says no"these are fake items as far as i can tell,AD's markings are generally very clear and white. pins seem to be rough and the logo is all messed up..

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 07:24:48 pm
content: Quote from: slurry on May 27, 2015, 07:15:25 pmHow to check then? If it is about within spec I will still use them as-is. Those 736's are not cheap.

author: wraper
author_rank: Unknown
timestamp: May 27, 2015, 07:36:49 pm
content: Quote from: technix on May 27, 2015, 07:24:48 pmThey are cheapest and crappiest opamps which likely will kinda "work" instead of 736,howthey will works is another question. So what if they were expensive? That means only that you paid a lot for fakes, not that they are "good" fakes.

author: wraper
author_rank: Unknown
timestamp: May 27, 2015, 07:45:42 pm
content: http://zeptobars.ru/en/read/OPA627-AD744-real-vs-fake-china-ebay

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 07:45:53 pm
content: Quote from: wraper on May 27, 2015, 07:36:49 pm736 is not op amps but true RMS converters. That'd be my concern.

author: wraper
author_rank: Unknown
timestamp: May 27, 2015, 07:54:11 pm
content: Quote from: technix on May 27, 2015, 07:45:53 pmThenifthey work, likely are some Chinese clone. OP2177 likely are just something else inside.

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 08:10:34 pm
content: Quote from: wraper on May 27, 2015, 07:54:11 pmWithout precision instrument, what specs can I use to check if it is not LM358 or TL082 inside? I used to check my OP07C by GBWP, by attempting to run 1MHz through it at gain 2, which will success on both TL084 and LM358 but fail in OP07C.

author: tom66
author_rank: Super Contributor
timestamp: May 27, 2015, 08:17:26 pm
content: Quote from: technix on May 27, 2015, 08:10:34 pmWhy would you bother?The chips are clearly fake.No one goes to this bother to rebrand identical parts.Write the purchase off as a loss, and take it as a future lesson.It would be very hard to qualify things like input bias current, distortion figure, offset voltage, etc. without precision instruments.

author: technix
author_rank: Super Contributor
timestamp: May 27, 2015, 08:42:15 pm
content: Quote from: tom66 on May 27, 2015, 08:17:26 pmIf you know my situation there "write off as a loss" isn't really an option and attempting to buy genuine chips is not really an easy thing to do, especially in China where major suppliers just began their business and even for genuine chips (like 74HC245's from Hitachi) can be a few times more expensive from Mouser or Farnell.

author: Richard Head
author_rank: Frequent Contributor
timestamp: May 28, 2015, 06:19:21 am
content: This is just a flyer, but did you buy them on ebay?

author: technix
author_rank: Super Contributor
timestamp: May 28, 2015, 08:34:59 am
content: Quote from: Richard Head on May 28, 2015, 06:19:21 amTaobao. I asked the supplier and they claimed that their chips are genuine. Then I pressed them into agreeing to refund if it failed sanity checks. I a going to check their GBP and voltage swing on this thing, as well as distortion figure.

author: Richard Head
author_rank: Frequent Contributor
timestamp: May 28, 2015, 09:27:24 am
content: This is the reason I only buy components from reputable distributors. However, having got on my ivory tower I must admit that even the "reputable" distributors have once suppled me a counterfeit component (that I know of).

author: technix
author_rank: Super Contributor
timestamp: May 28, 2015, 11:56:57 am
content: Quote from: Richard Head on May 28, 2015, 09:27:24 amMy problem is that those reputable distributors are out of reach...

author: Len
author_rank: Frequent Contributor
timestamp: May 29, 2015, 12:35:39 am
content: Quote from: technix on May 27, 2015, 08:10:34 pmSo you don’t know what those chips are but you still want to use them.The only thing that makes sense is to test them in your circuit (or a simplified version of it) and measure the parameters that matter to you, whatever those are. There's no point trying to guess what the chips really are or deriving their specs, that's a waste of time.Keep in mind that you will have to test every batch of chips you buy. Even if the supplier is the same and the part numbers are the same, what’s in the fake chips can change every week.

author: daqq
author_rank: Super Contributor
timestamp: May 29, 2015, 08:35:43 am
content: QuoteThere are parameters that are a dead giveaway if the "replacement part" is extra crappy - input current, offset voltages and such, but if they are in the same general area, well, that's a problem.One way could be to compare it against a known real one - measure each parameter (supply current included ) for many situations and if the parameters are off enough, then you probably have a fake part. However this is not 100% obviously. And you do need SOME precision instruments.But if in doubt, DON'T use the part - even if the parameters check out it could be a factory reject, something prone to failure, something very similar.

author: technix
author_rank: Super Contributor
timestamp: May 29, 2015, 08:49:04 am
content: Quote from: Len on May 29, 2015, 12:35:39 amFor OP07C my test circuit was a very crude PMOS low drop-out regulator, with an extra gain stages (2N7000 level shifter have some gain, as well as the main IRF4905 pass transistor) to make it even more oscillation prone. LM358 and TL082 both will cause oscillation but OP07C won't due to it not having enough gain in that ~600kHz frequency. This GBP trick won't work on OP2177 since it have 1.2MHz GBP which is very close to LM358. Can I check this my measuring its offset voltage using my "known good" OP07C or TL084?

author: technix
author_rank: Super Contributor
timestamp: May 29, 2015, 01:51:38 pm
content: Quote from: blueskull on May 29, 2015, 12:15:40 pmADI free samples for students requires professor's letter of recommendation in China and since I am not a student major in electronics engineering obviously I won't get one of those. Elememt14 is still a little bit out of reach for me for experimenting.

author: amyk
author_rank: Super Contributor
timestamp: May 29, 2015, 02:06:14 pm
content: Quote from: daqq on May 29, 2015, 08:35:43 amOr not, depending on how you look at it...IMHO it's a bad idea if your design relies on being right at the edge of datasheet tolerances, even if you get genuine parts.