How to tell a real opamp from a fake one

[@rogrevs]

Thanks for posting this video Eddy. A couple of years ago when I first got into synth DIY I bought a stack of TL07X and TL08X op-amps from Chinese suppliers on ebay. Then I read online that they may fakes, so I put them in a box and bought from some local UK suppliers instead. I came across the box at the weekend and decided to submit samples of both my UK and Chinese-supplied TL07/8 op-amps to your test. All the UK ones passed the test. All the Chinese ones failed the test --- TL071, 2 & 4 plus TL082. 80 fake op-amps going in the bin! I am now looking at what I have left in the box (LM358, LM324 & LM741) and trying to decide whether to bother researching a test for them or just stop wasting my time and bin the lot. Edit: I just noticed that IMSAI Guy did a test for fake LM741s using just a multimeter. My UK stock passed, Chinese stock failed. Another 10 op-amps in the bin!

[@EdEditz]

Well I have ordered ICs from ebay that turned out to be good but it's a rarity. I would test them though before throwing everything away.

[@rogrevs]

@@EdEditz I have bought logic chips from China that seem to work OK for my applications, but I haven't pushed them to their limits. I also bought a bag of cheap 2N3904 transistors that I use for creating noise circuits --- much better than my UK-sourced ones for that job. I won't be buying more op-amps though.

[@EdEditz]

@@rogrevs Yeah with transistors and diodes and zenerdiodes that I got from eBay I never had any problems either. I built my whole synthesizer using those and also all my resistors come from eBay/Chinese sources and they all work fine. Although what they call 1% tolerance on their blue metal film resistors is more like 3% but that's still good enough for what I use them for. I have had problems with a random gates circuit that would fall back to a certain pattern instead of being random and that was caused by a fake chip. Getting a good one in there solved the problem. I also mentioned that in the article I wrote about it.

[@leiferickson3183]

Wow! This might be the perfect op-amp for a rat pedal build! Plenty of slew rate limiting.

[@EdEditz]

Yes but the slew rate limiting is pretty high up in the audio spectrum so I don't think it'll be that effective on its own but as part of the RAT circuit it might work very well.

[@cuxsia]

Thanks ed for this., please allow me a question. I see the fake one has a poor bandwidth, does this affect for audio application?, I ask this because for audio we tipically use frequencies up to 20KHz. does this poor bandwidth affect somehow the performance of audio filters, preamps or equalizers?, thanks!!

[@EdEditz]

If you want to be sure you get the best audio quality then I would advise to use real chips. It's not only the bandwidth. Fake chips can be noisy too. I build a lot of synthesizer modules and they operate in the 20Hz to 8kHz range and for that they will usually be fine (especially for LFO's) but with filters you can get resonance or self-oscillation that is upto 20kHz and for that I would avoid using fakes and get the chips from a reputable source and not sites like AliExpress.

[@AdamTheAd-vanc3d]

Thanks for sharing this Eddy I have often wondered on how I could test an op amp. I guess you could always try the " avoid ebay" approach. However sometimes ita just pot luck.

[@EdEditz]

Yes it's usually the case ithat if they are too cheap to be true, they're fakes. I've had many good opamps from china on eBay but those were a little more expensive than on aliexpress. Just don't buy any chips from aliexpress

[@jeffersonavila7275]

Good day, can i know the schematics of your setup

[@EdEditz]

It's just a 12 V powersupply to pins 4 and 11 and pins 1 and 2 are connected together and signal on pin 3. The rest is not connected. Measure from pin 1.

[@gervaiscurrie6675]

I wonder what factors come into the difference between 'real' & 'fake'? If the faker has the chip die image & a Fab plant surely it's a 'Clone Fake'; if, let's say a generic 741 is re-badged/engraved as a faster FET TLO71, then its a real fake ? Am I along the right lines here??

[@EdEditz]

I think you're right. It's just chips with lesser specs being sold as higher quality than they are.

[@gervaiscurrie6675]

​@@EdEditz Yes - 'Passing off[..

[@ovi_4]

I have always purchased over the years OP-AMPS from various sellers on E_Bay. Lots and lots of them. But guess what! I just made a similar testing rig and tested a huge amount (about 300+) op-amps that I still have and....surprise surprise....only 21 are genuine out of the whole lot. I just cannot believe how naive I was buying such rubbish??? Woawww...!!!! Well, lesson learned and....Never again.

[@EdEditz]

Well you're not alone in that. I fell into the same trap when I first started out building synthesizer modules. The thing is, the fake ones work just well enough to let you not notice they are fakes. At least with audio circuits. That is until you test them. But sooner or later you learn that if you want good IC's you have to buy from reputable sources.

[@ovi_4]

@@EdEditz You are spot on. From now on: Only reputable sources for any components, not just ICs. I've noticed fakes on a lot of electrolytic caps as well as resistors that claim to be low percentage tolerance when in fact they are not, h and medium power high-frequency transistors as well. So... enough is enough. I'm gonna have to bite the bullet and fork out more money for anything that I will buy but with the assurance that I'll get what I'll be paying for. Tnx for such an eye-opener video.

[@dragonstuff1983]

Oh man.... I'm dealing with this now, I think. Do you have the circuit diagram so I can test a few out?

[@EdEditz]

Hi Adam. Just go to this link and scroll down a bit to the "Voltage Follower" section. It's really simple. The waveform signal is on the plus (non-inverting) input and the minus (inverting) input is connected with a wire to the output. That's all. www.allaboutcircuits.com/video-tutorials/op-amp-applications-voltage-follower/

[@dragonstuff1983]

@@EdEditz Thanks!