#1625

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IMSAI Guy

Күн бұрын

Episode 1625
let's see what my 'TL072' parts can do
Board: www.pcbway.com/project/sharep...
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Пікірлер: 99

@IMSAIGuy 10 ай бұрын

with help from W2AEW's video #215 and some more testing of parts. I can now say my 'TL072' parts are remarked LM358 op-amps which suffer from crossover distortion (yes even legit ones!). The parts are useable but only when you add a 1K resistor from the output to the negative rail to keep the LM358 from floating during the crossover. I'll do a follow up video someday. LM358 parts are useful in single supply circuits where you need to come close to ground. Crossover distortion is pretty rare in more modern op-amps. Oh, and a LM358 is way slower than a TL072, so there's that too

@absurdengineering 10 ай бұрын

LM358s are good parts for many things - just be familiar with their internal schematic. A lot of details that the datasheet only mentions by numbers (or mentions by not mentioning) become obvious. For one thing, they’ll just about murder anything past 10kHz at gain one. With gain>1 they are OK for low frequency work when their offset drift is compensated or doesn’t matter. Using two or more from the same package in a way that adds offset to both the signal and its reference compensates a lot of offset drift. They also don’t have enough gain in the output stage so in any application where you care about AC performance - especially stability (!) - you have to use their output stage in class A configuration, with a follower buffer added. It’s their “claim to fame” to start performing less horribly with a follower on the output. Even better if the 358’s output is loaded with a current source. Also it helps to use them in inverting configuration so that the dismal CMRR doesn’t suck what little performance they got. But any of that only matters when you design for a “wide open” hobbyist market where all someone may an ave access to is fakes with an LM358 inside. For anything else - any rail-to-rail cmos op-amp designed in the last 20 years has them beat. In performance. Not necessarily availability.

@sud9320 10 ай бұрын

I actually have a whole bunch of fake TL072's from 2 different suppliers but none of mine come close to de ground rail. So I'd say you can't predict what you are getting when you buy these.

@IMSAIGuy 10 ай бұрын

@@sud9320 yes, there is no way to tell

@alexloktionoff6833 10 ай бұрын

Please make a video, does 1k resistor workaround work for you or does't kzfaq.info/get/bejne/jM2fl7ylzqrDdmQ.htmlsi=sZwA6x0yMqUdd4N0&t=470

@w2aew 10 ай бұрын

Crossover distortion - looks like LM358. I did a video on this (#215 on my channel). Adding a DC offset to the signal could help to, to keep the output stage from hitting the crossover point.

@davidknightaudio934 10 ай бұрын

my thoughts exactly

@IMSAIGuy 10 ай бұрын

I didn't even consider them being single supply parts. I'll have to run some tests with the mindset of 'wow I can have as many LM358 opamps I want for free!"

@viperwizard491 10 ай бұрын

run OP in A class, but it wont be low power enymore

@tvelektron 10 ай бұрын

If it is LM358 or similar it may be a very useful part. With single supply it can reach negative rail on the input with no problem or malfunction. Also on the output it will go near the negative rail, good enough to drive a microcontroller input just for example. I still use this part in comercial products - it is cheap, easy to use (within ther limitations of course) and no delivery problems or delays at all as there are still different manufacturers.

@M0UAW_IO83 10 ай бұрын

I wondered if that was the case, googled for LM358 crossover distortion and the first video hit was your #215

@bobweiss8682 10 ай бұрын

Perfectly good---for soldering practice.

@argcargv 10 ай бұрын

I got some TL072 Chinese parts that turned out to be decent LM358 op amps (actually if I remember had slightly better slew rate than some old stock real LM358's). But in most respects (including the cross over distortion) they behaved the same as the LM358. But this could actually be very useful if you understand what the LM358's were designed for. They are best in single ended applications and are designed to be able to push the output close to the 0v rail. They are slow so they are good for low speed servo control. For example, they would be excellent application to an adjustable constant current load where the voltage drop across the sensor resistor would be attached to the ground rail. In single ended applications you can usually set up the circuit so that it is only sinking or only sourcing current and in that case the cross over distortion is not an issue. So I bet these would be very useful in low speed servo control type applications using single ended supplies. In fact, I suspect they would be good replacements for LM385 op amps if you were in a pinch.

@IMSAIGuy 10 ай бұрын

others have suggested they are 358 I'll have to do some tests

@absurdengineering 10 ай бұрын

LM358 got about 50uA of sink current capability for outputs below 0.7V or so. It really helps loading it some more with an external current sink so the output stage runs class A. It will then happily drive AC down to 0.1V or so.

@ats89117 10 ай бұрын

They should be good for experimenting with, like see what happens if you put 5,000 volts across them!

@micc1211 10 ай бұрын

Could you use them as comparators so you only care about pegging to the rails and not amplification?

@dorelgogu8631 10 ай бұрын

I did it and is ok at low frequency.

@absurdengineering 10 ай бұрын

LM358 are horrible as comparators. There’s no point to using them in that role. LM311/393/2904/2901 are same vintage, same process, same price, but much faster and have some nice properties “at the edges” of specified operating conditions.

@noneofyerbeeswax8194 8 ай бұрын

At 100 Hz, maybe. Their slew rate is horrible.

@vk3zen-rfdesign980 10 ай бұрын

there is a guitar distortion preamp that uses TL072 s and the dirtier the better ...they would work fine in that

@Peter_A1466 10 ай бұрын

But with this behavior they are not genuine TL072s

@t1d100 10 ай бұрын

The broader question remains... How to use inferior parts of any ilk? As I see it... Firstly, it would never be advisable to use them in a commercial product. Secondly, you will need to invest the time and effort to a) characterize how the part performs and b) confirm that performance is consistent throughout your stock. Or, donate them to your local makers group to practice soldering, a use which should not be underestimated, IMO. Cheers!

@djfwalker 10 ай бұрын

Its reputable suppliers for me from now on, no more ebay gambles

@Amplified208 10 ай бұрын

Wow, that is very sad to see, considering that a lot of hobbiest rely on cheaper Chinese components sometimes for small projects.

@samreames1713 10 ай бұрын

Which is why I test ALL chips from china in a basic test circuit and find almost 20-30% of them bad. I recently received a lot of JFET transistors that turned out to be BPJ NPN transistors!

@paulperano9236 10 ай бұрын

There are other OpAmp functions that these may be OK for. For those on limited budgets they could be ok for things like splitting a single power rail to a dual power rail.

@yurkshirelad 10 ай бұрын

I bought some TL072s from a reputable Canadian dealer and they all had crossover distortion. The schematic I was working from to learn didn’t work properly, so now I’m wondering if they unknowingly sold me some dodgy clones.

@edgeeffect 10 ай бұрын

... or some miss labeled 358s?

@absurdengineering 10 ай бұрын

TL072s should be fairly smooth on the output as it crosses mid-supply (usually 0V). Common mode must be 2V or higher above negative rail, and output can be about 2-3V from either rail at the closest. Pretty nice parts for interfacing with germanium PNP analog circuits that work up to positive rail :)

@uni-byte 10 ай бұрын

I guess you could use them as comparators or make funky relaxation oscillators out of them .. as long as waveform was not crucial.

@andymouse 10 ай бұрын

Comparators was my only thought...cheers.

@TheDefpom 10 ай бұрын

Can probably use them as a comparator, that may even e what they are, possibly a Schmitt type.

@Enigma758 10 ай бұрын

I suspect they might be OK for some low precision STEM projects such as an op amp based line following robot.

@OneBiOzZ 10 ай бұрын

Well they clearly have a use, to trick people in to buying them and spending hours tracking down the weird distortion

@reedreamer9518 10 ай бұрын

Interesting as always.

@florabee9283 10 ай бұрын

It would be interesting to see how they behave in place of the usual rc4558 in a tube screamer circuit- where the feedback is the pair of antiparallel diodes

@PF-gi9vv 10 ай бұрын

You could put 5 of these together and build a 10 bar/led driver display for audio level or voltage level indicator. A voltage divider with 11 resistors in series will give a reference for each op-amp.

@1kreature 10 ай бұрын

Sounds to me like they are just comparators :p

@Manf-ft6zk 10 ай бұрын

As mentioned it looks like the transition from positive to negative output current is not well adjusted. To much gap in the so called "Class AB Control Circuitry" at the output. The tests made were symmetrical for the input and the output. As the amplifier has two input stages, one for high and one for low common mode signals this could also be the source of failure. One could still find out whether it is the input or the output that has the transition gap. There are applications like regulating power supplies where there is no zero crossing and they should be able to work normal. But with the price of those components today I would just get new ones to replace them in the drawer for the next 10 years.

@ivolol 10 ай бұрын

Someone gotta make a video comparing 16 different sources of LM358 someday. See how they all compare. NOS, Chinese OEMs, different western OEMs, fakes.

@IMSAIGuy 10 ай бұрын

www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/msg3545907/#msg3545907

@christatler7378 10 ай бұрын

They would work well as comparators. What about trying them with single rail power supply?

@EdgarsLS 10 ай бұрын

You could operate them in class A, to get around the crossover distortion. Load the output to the negative rail externally with a resistor or something, then bias it around 3/4VCC, towards the positive rail. That should have no crossover distortion since only one of the output transistors is working (the positive side in this case). Then also use it only as an inverting amp, since the CMRR is most likely pitiful. So with all this it might work good enough for an audio amp

@noneofyerbeeswax8194 8 ай бұрын

LM358 and audio should not be put in the same sentence. Their open-loop gain rolls off at 10kHz, so they can't even cancel their own crossover distortion, much less so higher order harmonics. They're only good for general purpose, ground-referenced DC applications. That being said, I have used LMV358s in limited-bandwidth (8kHz) mike and headphone preamps designed for speech only. They at least have a class-B output.

@chupathingy5862 10 ай бұрын

Might be good for an audio effect. Then again, I'm into harsh noise, so...

@KeritechElectronics 10 ай бұрын

Good for noise generators, eh? This reminds me to get a good function generator when I get my payout. Sine wave only is no longer good enough for me, haha!

@AnalogDude_ 10 ай бұрын

a couple of years ago, i made a similar pcb for opamps with bypass caps and it fits on a breadboard, about an inch long and slightly wider than opamp due to the bypass caps. 3:23 that looks like the zero crossing of totem pole transistor arrangement, but the bases aren't properly biased. It seems who ever made these doesn't have the skills of tools to trim onboard resistors, capacitors.

@absurdengineering 10 ай бұрын

Oh they had skills but laser trim in the 70s was expensive :)

@AnalogDude_ 10 ай бұрын

@@absurdengineering You think these Chinese opamps from the video where made in the 70ties? There is this known guy who has a Tube channel en reverse engineer silicon, he showed how they do it, it's more or less a path you cut off.

@absurdengineering 9 ай бұрын

@@AnalogDude_ laser trim was super expensive back then. It is cheaper today - but when you’re making fakes, why bother trimming them? Saves half a cent per part or whatever. I guess my weird sense of humor doesn’t come across very well.

@portblock 9 ай бұрын

Could you use them for DC stuff like followers/amplifiers? example would be current measurement (amplifier) or follower for ADC , slow peek detection?

@IMSAIGuy 9 ай бұрын

they turned out to be LM358

@user-lg3bw2ol9x 10 ай бұрын

What about open loop comparators or Schmitt trigger comparator?

@superpie0000 10 ай бұрын

definately good for audio effects synthesizer stuff, distortion is cool😎 i would try not to sell a product with this in it tho unless i can make sure they dont randomly die-not gonna happen

@hydromakers 10 ай бұрын

If you increase your feedback resistance to maybe (20k - 200k) would that get rid of the cross over distortion?

@ZPapaGeek 10 ай бұрын

Could make an interesting guitar distortion pedal?

@jimomertz 10 ай бұрын

Maybe don’t use a split supply? Wouldn’t that eliminate the crossover distortion? They just look horribly slow too. Maybe only good for amplifying DC 🙂

@ludmilascoles1195 10 ай бұрын

You can use them for majik smoke generator?

@frankowalker4662 10 ай бұрын

You could make some interesting guitar FX pedals.

@sud9320 10 ай бұрын

I accidentally bought a bunch of these fake TL072's for my DIY modular synth. They are horrible for audio frequencies but in most cases they are great for CV (sub audible) frequencies. So I still use them all the time! :)

@electronics.tinker 10 ай бұрын

I am not quite as negative about these Chinese parts kits. It's definitely true that you don't know what you are getting so there is a risk. When I was starting out, I bought a kit from Amazon with 120 pieces of various ICs: a few types of op amps, Darlington pairs, LM386, comparators, and one kind of opto coupler. In every case so far, parts from this kit have operated OK as *some sort* of part of the right sort. For example, the kit includes op amps marked NE5532P. These op amps are definitely *not* NE5532P's. They have less bandwidth and a lower slew rate-- but they work much better than the Chinese op amps you tested. In a 10x inverting amp configuration with a 1V input, they look fine with a 50 kHz input triangular wave. For casual educational experiments using a generic op amp without pushing it, they are fine. I got a bunch of parts to play with and learn from for a very low price. But it is definitely a case of caveat emptor, and you need to plan to test the parts to see what they can do-- and don't pay too much! Amazon lets you return stuff if it disappoints too much. BTW, your channel is one of my favorites-- so thanks!

@ralphj4012 10 ай бұрын

Not a total loss, good for 100 flashing festive LEDs (assuming that you don't already have the flashing types or any retail stores nearby).

@edgeeffect 10 ай бұрын

I'm fooling around with old telephones so low frequency audio amps would be OK for that....... IF you could get a decent voltage through them.

@williamkohl8081 10 ай бұрын

maybe use them as comparitors

@vladnurk4710 10 ай бұрын

5 dollar for the board shipping 53 dollar +

@gamerpaddy 10 ай бұрын

theyre not bad, they are "differently coloured" and have character". you could put them in a metal box with oversized toroidal transformers and stupid amounts of capacitors, then sell it as sliced bread and hot cakes in the audiophile community claiming to hear the world of difference lol

@Amplified208 10 ай бұрын

Lol

@Paxmax 10 ай бұрын

"...has excellent classic Class B audiophile quality..."

@KeriRautenkranz 10 ай бұрын

Your cunning plan won't work. Reason? These components will actually make a noticeable difference that anyone can hear. Audiophiles hate that!

@SergiuCosminViorel 10 ай бұрын

The thing is all Hi-Fi systems are made with Chinese IC, so this presentation may very well be something else. Am thinking, maybe the ICs you tested here, pretending to be Chinese, maybe they are made in Malayesia, Taiwan, Turkey, and is just a targetted denigration video. I do not know about TL072, but i know about some others, LMs, if you have a good sound system, it is made with Chinese LMs. As i said, targetted denigration, when the ICs you tested, can very well be made in USA. It is, after all, a marketing technique invented by USA, not by China, to make bad electronic devices, sell them, pretending they are made by enemies of USA, to train consumer to buy electronic devices at exorbitant prices.

@nickcaruso 10 ай бұрын

One thing I'm curious about -- what is actually in these bad op-amps? Are they repackaging old parts by changing the labels, or are they actually manufacturing bad stuff?

@IMSAIGuy 10 ай бұрын

some guesses are re-marked LM358 single supply parts. I'll be doing a follow up video

@nickcaruso 10 ай бұрын

@@IMSAIGuy looking forward to it. So if I want TL07x/8x parts for a synth project, I should just buy them from ... digikey? Mouser? Any recommendations?

@IMSAIGuy 10 ай бұрын

@@nickcaruso those two places are good

@jj74qformerlyjailbreak3 10 ай бұрын

Amazon is just as bad if you don’t know what you are buying. I quit buying off eBay unless it’s something specialized. Usually after spending time hunting something down I can’t find, I stumble across it in the wild.

@TheEmbeddedHobbyist 10 ай бұрын

Just take the hit and throw them in the WEEE bin.

@IMSAIGuy 10 ай бұрын

no hit, refunded my money, they are free

@andymouse 10 ай бұрын

Howdy Squeak !

@TheEmbeddedHobbyist 10 ай бұрын

@@IMSAIGuy Once you know there is issues with them it's just not worth the effort of using them. a day, a week later the x-over may have moved somewhere else. i've given up buying active components from Fleabay etc.

@TheEmbeddedHobbyist 10 ай бұрын

Well howdy yourself@@andymouse

@inerlogic 10 ай бұрын

50? Redo your 100x gain bandwidth test with each having a gain of 2, lol....

@monchiabbad 10 ай бұрын

Do a batch check to see if this chip was a fluke or most the others have the same problem

@IMSAIGuy 10 ай бұрын

they be all bad

@monchiabbad 10 ай бұрын

@@IMSAIGuy im just wondering if they all have the same defect

@jack002tuber 10 ай бұрын

My luck is I get 100 of these on ebay

@SergiuCosminViorel 10 ай бұрын

if you test yours, maybe they are perfectly good

@darnokgr 10 ай бұрын

This "funny" behaviour may have some positive usage! Well, in the guitarist world, if you have something different from another 100k guitarists, than this could be considered as a "feature not a bug". Lets say you use it as hi-gain distortion or overdrive circuit with diodes to ground in output or with diodes in feedback loop. Then this "assymetry" could be utilized as 'ekhm' "specifically sounding feature that nobody has". Sounds like "MILLLLLLION DOLLLLARS :)". Yeah, not all guitarists are audiphiles in common sense, but AUDIOPHILES in THAT sense. IMO, try using it in simple audio application or "guitar effect" if you wish to see it that way! Then these are not garbage anymore, they are my precious :)

@Tibbon 10 ай бұрын

I don't get it. Making your own op-amp in bulk seems to be quite a process. I can solder up some discrete ones, but not in a chip package! Why in the world don't the engineers making these (who obviously have some skill) do it right? It isn't like the TL072 isn't well documented, and if you're already fabbing a chip, it doesn't seem to save cost to do it wrong.

@Tibbon 10 ай бұрын

I'd love to see an interview with someone who designed these.

@__--JY-Moe--__ 10 ай бұрын

Oh-pampers! 4 new & old!! by golly, he's a regular genius! just look @ all this talent flowing out of him! congratulations Son, U'r a genius!! now he sew's it up with this! amazing! we'v been warned! don't buy junk chips!

@brianbrumfield3330 10 ай бұрын

Stop supporting the people who sell fake parts! Maybe you got your money back but nine other buyers didn't feel it was worth the trouble.

@RonDogInTheHouse 10 ай бұрын

Agree. I think the usefulness of these parts has been identified. They off-loaded their piss poor product and extracted money from the US. Score China Export..... or, is it..... China import?