Author Topic: Can Dave make a video comparing EBAY OP-AMPS to real ones  (Read 2702 times)

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Offline MathWizardTopic starter

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Can Dave make a video comparing EBAY OP-AMPS to real ones
« on: March 22, 2023, 12:56:33 am »
Some chips on ebay, Aliexpress,  amazon, etc are a lot cheaper than the real thing, and what are people really getting?

I know ebay is not a recommended source for genuine parts. But has anyone done a video, comparing common ebay chips, like op-amp's, to some real ones ? I suppose it could change week to week, but someone with a lot of knowledge and equipment should do a video comparing some.

Like toady I want to get some OP07 op-amps, and I see some cheap ones on ebay. I guess they could be anything, but if they are at least clones, well how good are they ?

But some factories must make clones of chips, and try to make them work the same. There can't be that many places making copies of op-amps.
 

Offline Ed.Kloonk

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #1 on: March 22, 2023, 01:01:43 am »
I'd go a step further and suggest examining the impact it might have on a beginner doing most of the prudent things such as reading up, following examples on youtube and on the web and then wondering why their circuit doesn't work properly because they bought lousy parts.
« Last Edit: March 22, 2023, 01:04:53 am by Ed.Kloonk »
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Offline james_s

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #2 on: March 22, 2023, 01:18:43 am »
Somebody was decapping and posting die pictures a few years ago. IIRC most of the knockoff op amps are some basic jellybean part like the LM358.
 
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Offline John B

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #3 on: March 22, 2023, 02:03:38 am »
Unless the end goal is to purchase such things off ebay, it's a waste of time and worse still, encourages their sale on both the buyer and seller side.

If you are specifying an OP07, why would you want anything other (read: inferior in performance) than an OP07? They're still jellybean enough that the legit part is reasonably affordable on somewhere like LCSC.
 
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Offline Someone

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #4 on: March 22, 2023, 03:14:39 am »
If you are specifying an OP07, why would you want anything other (read: inferior in performance) than an OP07? They're still jellybean enough that the legit part is reasonably affordable on somewhere like LCSC.
Depends what specification is important, as there are many manufacturers of OP07:
https://www.lcsc.com/product-detail/General-Purpose-Amplifiers_Hangzhou-Ruimeng-Tech-OP07_C1508997.html
That isn't going to be a drop in replacement for a different brand OP07 in all applications (worse in some areas, and better in others), equally applies between TI and AD parts.
 

Offline John B

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #5 on: March 22, 2023, 05:03:43 am »
Not sure what the argument is though, you have a datasheet to get specs from to determine what you need. I purchased my TI OP07s off LCSC a while back and they were quite comparable in price too. On ebay, all you will get is the part number and even that will likely be a lie. For example, if you try to purchase a TL07X opamp on ebay, it's likely to be some unknown bipolar opamp. What's the point looking there if you won't even receive a JFET input opamp?

It would be a lot more palatable if things were listed as "OPAMP LUCKY DIP", and it was priced accordingly. But as it stands, at lot of the fake ebay parts end up being as expensive or more expensive than something off LCSC.

I have one caveat. I will say that I have found roll packaged SMD items on ebay to be a safer bet. These were parts like XLSEMI DC/DC converters, IR2117 gate drivers, TL494. Legit as far as I can tell. However as mentioned before there is no monetary incentive to take the risk. Loose packed DIP packages seem to be the more commonly faked devices.
 

Offline james_s

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #6 on: March 22, 2023, 05:22:30 am »
A problem with even having these fake parts around is they get mixed into your stash and then they can end up in various projects with you wasting time trying to figure out why it isn't working. I went through my parts bins a couple years ago and threw away most of the obviously fake or suspect ICs.
 

Online Gyro

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #7 on: March 22, 2023, 01:38:43 pm »
It seems a little pointless / impossible to make a video, as the jellybean opamp (assuming that it even is an opamp) is likely to change with whoever is faking (re-marking) them and what trash parts they have available at the time.
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Offline thm_w

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #8 on: March 22, 2023, 09:59:54 pm »
It seems a little pointless / impossible to make a video, as the jellybean opamp (assuming that it even is an opamp) is likely to change with whoever is faking (re-marking) them and what trash parts they have available at the time.

Yeah, although it is kinda fun if its a "figure out what part this is" but that is better with die shots as mentioned above.

The LCSC parts testing was mentioned in a previous thread and would be a bit more interesting. eg testing extremely cheap off-brand FETs/opamps/etc that have specs that seem to good, see if they actually meet them or not.
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Online Bud

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #9 on: March 22, 2023, 10:06:24 pm »
Video comparing what? The entire set of datasheet data? This is a hell of a work.
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Offline DimitriP

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #10 on: March 22, 2023, 10:31:19 pm »
Quote
I know ebay is not a recommended source for genuine parts. But...

It's great that you know that.
No but.

   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline Whales

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #11 on: March 22, 2023, 11:24:45 pm »
Somebody was decapping and posting die pictures a few years ago. IIRC most of the knockoff op amps are some basic jellybean part like the LM358.

That might have been me.  Other nice people contributed their own die-shots at the end:

https://www.eevblog.com/forum/beginners/opamp-input-offsets-working-in-the-opposite-direction-to-what-i-expect/

I also have some decapping process pictures on my website:

https://halestrom.net/darksleep/blog/038_fakeopamp/
« Last Edit: March 22, 2023, 11:33:00 pm by Whales »
 
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Offline DimitriP

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #12 on: March 23, 2023, 02:09:40 am »
On ebay they sell  $2.16 for 10 pieces
Mouser prices for the TI part are between $5.52 to $26 for 10.
If someone would just validate the ebay parts for free, think of the savings!!!
 
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Online EEVblog

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #13 on: March 23, 2023, 03:05:15 am »
It's actually a lot of work to do this properly. Every spec, or at least allthe major ones would have to be tested over mutliple units and over temperature.
And then you might have multiple fakers using multiple processes.

More interesting to review at least name brand low cost asian parts, like this:


That being said, that video got a decent amount of hits. Might be worth doing more...
« Last Edit: March 23, 2023, 03:07:36 am by EEVblog »
 
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Offline Swainster

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #14 on: March 23, 2023, 03:46:58 am »
I personally dont think it's worth taking the risk on a jellybean like OP-07, but I will admit to taking a punt on more expensive or obsolete components. Particularly for the latter, eBay may be one of the only options.

So far I've mostly stayed away from China ebayers for ICs, unless I can tolerate the risk e.g. I bought a kit of generic DIP ICs including a number of op-amps, just for playing around with. I wasn't really bothered about fakes - in fact discovering the fakes would add to the entertainment value of the kit. As it turns out, going by slew rate, the LM358/324s were unsurprisingly a good match for standard parts, and I seem to recall that the 741 was a good match too. The NE5532 was obviously fake, but interestingly it was not a repackaged 358. It was more like a 4558.

Maybe a video on how to quickly check if an op-amp is genuine would be useful? The slew rate test I used is dead easy if you have a suitable sig gen and oscilloscope, and one is looking at lower speed op-amps, but there are plenty of other parameters which may be worth looking at. For op-07 the offset voltage would be the obvious choice.

Off topic, so far I have had good luck with resistors from China suppliers, and salvaged parts also seem legit (e.g. lm399s, OCXOs by the handful).
 

Offline MathWizardTopic starter

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #15 on: March 23, 2023, 04:08:19 am »
A lot of hobbists still buy from ebay/etc. So I wish someone with the know how, real parts, and equipment, would make some circuits and compare them. And make a video.

Are there really that many scammers on ebay though ? Some hobbyist with the same question needs to find out.

I could try making some circuits, but I hardly have any true brand name parts. In a circuit I made the other day, I saw no difference between a few BJT's and op-amps. But IDK if I really should have, or could have on my scope.


I need to lookup in the data sheets the test circuits for op-amps and make some proper test jig's, and see what I can see.

What about a LM723 from ebay. If it's a clone, are they any good, or garbage?


The big places like Mouser, etc, all charge too much. The electronics cartel is nickel and diming the little people to death.
« Last Edit: March 23, 2023, 04:24:05 am by MathWizard »
 

Offline james_s

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #16 on: March 23, 2023, 04:47:55 pm »
The big places like Mouser, etc, all charge too much. The electronics cartel is nickel and diming the little people to death.

Op amps from Mouser and other vendors are cheap, comparing them to counterfeit garbage is not a fair comparison. If you want to know how the ebay op amps perform, just grab the datasheet for the LM324, that or something similar is what most of the ebay parts are, but you never really know, you might buy the same part from 3 different sellers and get 3 different things. This is why it's pointless to even evaluate them, put some value on your time and frustration and just buy known good parts, don't support scammers.
 
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Offline DimitriP

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #17 on: March 23, 2023, 05:28:33 pm »
Quote
The big places like Mouser, etc, all charge too much. The electronics cartel is nickel and diming the little people to death.

Oh boy.
If you need 1000 of them thingies, TI willsell them to you for 0.33 a piece
From digikey, 1000 will cost you less than double at a whopping (!) $0.52 a piece

But if you need 1, it's a $1.15 with probably $8 shipping.
Someone has to pay the eelctric bill there too and the person handling the 1,2,3,4 pieces and the bagging and labeling and shipping and making sure you are getting the part you ordered and that's genuine and stock the other thousands of parts for all the other orders that come in.
In a perfect world we could all go out buy some OP07 seeds, water them and in a few short weeks have a OP07 bush. but this world is less than perfect :)
 :horse:


   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 
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Offline MathWizardTopic starter

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #18 on: March 25, 2023, 09:41:50 pm »
Well what about the OP07's on LCSC ? I'm new to LCSC and I see the TI or AD versions are $6.40 each, vs the Asian brand names that are 23cents.

So in that case, what are the copies like ?? I don't have any instrumentation op-amps, and I gather these are old and not too expensive.

What are some good, lower cost op-amps these days, to keep on hand, to handle different situations and needs ? I'm going to order some jelly bean ones, but there's 1000's of models out there I never heard of.
 
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Offline John B

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #19 on: March 25, 2023, 09:53:08 pm »
https://www.lcsc.com/product-detail/Precision-OpAmps_Texas-Instruments-OP07CDR_C7433.html

~27c AUD each in 150 qty.

Keep in mind that there's subtle variants of each chip that may or may not be relevant to you. Some of those variants are considerably more expensive due to supply/demand.
 
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Offline MathWizardTopic starter

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #20 on: April 03, 2023, 01:22:38 am »
I ordered some stuff from a few places, and in general I feel like a sucker, being taken as a fool, then add shipping and duty fee's, and I really should just stick to books and simulators.

So if you built a factory today, just to make quality op-amps, that have been around for decades, how much does it really cost to make 1 chip, and sell it ? Nevermind shipping


Even just TO-92 BJT/s FET's cost 0.5-$1 each just for decades old common models. That's crazy.

It's all run like a mafia I'm sure
« Last Edit: April 03, 2023, 01:27:10 am by MathWizard »
 

Online EEVblog

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #21 on: April 03, 2023, 06:42:32 am »
Well what about the OP07's on LCSC ? I'm new to LCSC and I see the TI or AD versions are $6.40 each, vs the Asian brand names that are 23cents.

So in that case, what are the copies like ?? I don't have any instrumentation op-amps, and I gather these are old and not too expensive.

Got any specific links?
 

Online EEVblog

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #22 on: April 03, 2023, 06:43:56 am »
https://www.lcsc.com/product-detail/Precision-OpAmps_Texas-Instruments-OP07CDR_C7433.html
~27c AUD each in 150 qty.
Keep in mind that there's subtle variants of each chip that may or may not be relevant to you. Some of those variants are considerably more expensive due to supply/demand.

Yes, you can pay a real premium for a selected part with known good offset etc. Same for voltage references and other parts.
 

Offline Shock

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #23 on: April 03, 2023, 12:14:49 pm »
You are also paying for someone to pick the part up off a shelf pop it into an esd bag and seal/label it. The cost of doing this along with business expenses are getting increasingly more expensive.

Avoid buying rubbish from china it only encourages them to make more fakes. What is annoying here is the local electronics retail stores are all filled with chinese rubbish as well. I'd rather pull something off an old board than pay for a no name or generic component.
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Offline james_s

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Re: Can Dave make a video comparing EBAY OP-AMPS to real ones
« Reply #24 on: April 03, 2023, 05:38:04 pm »
Packing materials are not cheap. I worked out at some point that it's cheaper to buy the cheapest of some part and throw it away in order to get the ESD bag and foam than it is to buy the bags and foam by themselves.
 


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