Dieshots: Opamp input offsets working in the opposite direction to what I expect - Page 1
Forum section: electronics / beginners

author: Whales
author_rank: Super Contributor
timestamp: September 06, 2019, 12:44:52 am
content: Edit: part appears to be fake, but not sure exactly what it is yet.dieshots on page 2.Take a simple split-rail non-inverting ~x100 opamp (TL074CN) amplifier:Now let's tie the input to GND (0v) through a resistor.I hope for 0V on the output, but know there will be some DC offset instead because of the opamp's input offsets.Now this is the part that confuses me:[Resistor tying input to ground (ohms)][Amplifier output (mV)]200K+30100K+7010K+160short+200The datasheet specifies a typical input offset of 3mV for this part, so for a x100 amplifier 200mV is within spec.What I don't understand is why making the tie-to-ground weaker makes the outputlessoffset. I presume that I'm just interacting with the input stages in an unusual way (ie this is caused by something not modeled by input voltage+current offsets)? I note that if you increase the tie-down impedance to 1M then the output swings to negative.

author: fourfathom
author_rank: Super Contributor
timestamp: September 06, 2019, 01:35:21 am
content: What is the value of that resistor from (-) input to ground? I can't tell.You do need to consider the input currents as well. This is why we try to match the resistance feeding the (+) and (-) inputs. The input currents flowing through a mismatched input resistance will result in an additional input offset voltage. This is probably what you are seeing.

author: Whales
author_rank: Super Contributor
timestamp: September 06, 2019, 02:46:18 am
content: Lower resistor = 1K.That would suggest the balance point would be around 1K on the non-inverting input?

author: fourfathom
author_rank: Super Contributor
timestamp: September 06, 2019, 03:09:24 am
content: Quote from: Whales on September 06, 2019, 02:46:18 amYes, it would. And I just looked at the input bias current and bias current offset for that opamp. It's in the 100 pA range, so with 1K input resistance the resulting input offset voltage would be perhaps 100 nV (insignificant here). And yes, the input offset voltage (typ spec around 3 mV) and your gain of 100 should give you around 300 mV output offset.But for now, let's assume that the offset voltage is the typical 3 mV, and that's what drives your 200 mV output. With 199K Ohms difference in the input resistance, the 100 pA input-current generated offset voltage could be as much as 20 mV. This more than puts it in the range to cancel out any input offset voltage.So I think that your input resistance mismatch just happens to cancel out the input offset voltage. If the offset voltage were zero, then the matched input resistors would give you a balance.I'm just guessing though.

author: magic
author_rank: Super Contributor
timestamp: September 06, 2019, 05:58:29 am
content: (200mV-160mV)/100/10kΩ=40mV/100/10kΩ=400µV/10kΩ=40nAThat's dangerously close to LM358/LM324 specs.We have already had similar threads here. Did you buy it from China?Post a picture of that thing.

author: Zero999
author_rank: Super Contributor
timestamp: September 06, 2019, 08:11:22 am
content: Quote from: fourfathom on September 06, 2019, 03:09:24 amYou've made an error with the decimal place there. 100*10-12*200*103= 20*10-6= 20µV.Quote from: magic on September 06, 2019, 05:58:29 amI agree, it might be fake.

author: Whales
author_rank: Super Contributor
timestamp: September 06, 2019, 08:39:52 am
content: Hmm, so you are suggesting that the effects of the input current offset are counteracting the effects of input voltage offset. That makes sense, they are supposed to be models of separate problems, so it would be valid for them to have opposing signs.Yes it's a cheap eBay-obtained part. I assume the TL07x family is cheap enough to not be worth faking.Not sure what you can really get from the pictures given how much variation exists across legit runs of parts. High-res attached, including a crude filing away of the epoxy.

author: John B
author_rank: Frequent Contributor
timestamp: September 06, 2019, 09:35:38 am
content: Quote from: Whales on September 06, 2019, 08:39:52 amhttps://www.eevblog.com/forum/beginners/tl07x-tl08x-ebay-fakery/msg2625603/#msg2625603Have a look here and see if your op amp exhibits similar behaviour. Most of interest would be the fact that bias currents are flowing out of the op amp.

author: StillTrying
author_rank: Super Contributor
timestamp: September 06, 2019, 09:39:22 am
content: Quote from: Whales on September 06, 2019, 08:39:52 amYes, you could usually just assume it's the bias current flowing through your tie-to-ground resistance causing a voltage at the non inverting input which is cancelling the 2mV offset at the inverting input. But for that to work with your mV measurements the input bias currents would have to be 100s of times higher than the data sheet says.I don't use those TL0xx op amps because the data sheets don't give any specs below +/- 15V supplies.

author: exe
author_rank: Unknown
timestamp: September 06, 2019, 10:39:24 am
content: Two more things may happen:1) damaged input (like damaged ESD diodes can contribute to input bias current), had such experience with NE5532 when I messed up with power rails2) oscillation. I'd check with an oscilloscope that there is no oscillation. May be this is less of an issues with TL07x devices, but I had this problem with NE5532 when I had "weird" offset. A decoupling cap solved this problem (it was on a bread board).Anyway, if input current in the order of tens of nanomaps, it's easy to measure it with a DMM.

author: Zero999
author_rank: Super Contributor
timestamp: September 06, 2019, 11:15:24 am
content: At room temperature, the input bias current (not offset current, which is the difference between theoffsetbias currents of each input) on the TL072 should be too small to measure using the current setting of an ordinary multimeter.One thing you could try is measure the voltage across the input resistor, at room temperature and after gently heating the TL072. It's a J-FET op-amp, so the bias current should have a positive temperature coefficient. If the current falls, after heating, then it's really a BJT input op-amp, not the TL072. BJT input op-amps have a negative temperature coefficient for bias current, because the hFEincreases with temperature, so the base current falls.

author: Whales
author_rank: Super Contributor
timestamp: September 06, 2019, 11:22:31 am
content: JohnB:thanks for the link to the other faked TL* topic. I was also thinking of hunting for class B crossover distortion, I believe the TL074 is supposed to be biased (AB) to prevent it.Zero999:Your temperature-based analysis technique sounds interesting. Surely this also depends on which way around the input diff pair has been constructed?exe:Already suspected those two causes. Tried changing it for another spare and tried adding 100nF to both inputs then outputs, no dice. StillTrying's explanation makes the most sense.

author: exe
author_rank: Unknown
timestamp: September 06, 2019, 12:14:54 pm
content: I meant decoupling to power rails.Also, unused opamps may oscillate, google "what to do with unused opamps".I suggest: 1) properly terminate unused opamps 2) measure input bias current with DMM.Actually, you can measure input offset voltage with DMM too, measuring a few mV of voltage is no problem, I did that.

author: Audioguru again
author_rank: Regular Contributor
timestamp: September 06, 2019, 12:21:02 pm
content: I also think you got a fake ebay TL074 that is actually a lousy old LM324:1) The LM324 has bipolar PNP input transistors and the TL074 has Jfet input transistors.2) The LM324 works fine with a supply as low as 3V and the TL074 needs a minimum supply of 7V (min 10V is recommended).3) The LM324 is very noisy and the TL074 is low noise.4) The LM324 has terrible crossover distortion and the TL074 has very low distortion.5) The LM324 has trouble above a few kHz and the TL074 works fine to 100kHz.

author: fourfathom
author_rank: Super Contributor
timestamp: September 06, 2019, 03:00:25 pm
content: Quote from: Zero999 on September 06, 2019, 08:11:22 amOops, thanks for checking! I was doing this with pencil and paper, which is usually a pretty good method for decimal placement. Apparently not this time. And there goes my "normal operation" theory.

author: Zero999
author_rank: Super Contributor
timestamp: September 07, 2019, 01:24:57 pm
content: Quote from: Whales on September 06, 2019, 11:22:31 amYes, you're right. The construction of the differential pair is the determining factor. The leakage current of reversed biased PN junction of a J-FET gate or MOSFET ESD protection diode has a positive temperature coefficient and the base current of the BJT has a negative temperature coefficient, as it's inversely proportional to the hFE, which has a positive temperature coefficient.The only difference between PNP./P-channel and NPN/N-channel devices will be the sign. The magnitude will be positive or negative depending on whether it's J-FET or BJT. The sign will be less predictable for MOSFET inputs because the leakage ESD protection diodes will dominate the gate leakage, but the magnitude will still have positive temperature coefficient.The exceptions to the above are rail-to-rail input or bias current compensated stages. A rail-to-rail input stage will have a mixture of both N and P devices and a bias compensated input stage will have internal current sources/sinks which cancel out the input bias current. It's highly unlikely a fake TL072 will be a more expensive bias compensated or rail-to-rail, so I think it can be ruled out.

author: Whales
author_rank: Super Contributor
timestamp: September 07, 2019, 11:41:18 pm
content: Crossover distortion & freq performance:Circuit used: x100 amplifier from first post. Output terminated 1K to 0V ground.The 10KHz output looks 3db (power) down from the 1KHz. In a x100 amp that would make more sense for a 1MHz part (LM324) than a 3MHz (TL074) one. (edit: should I be using db of voltage or power here? I've forgotten, may be wrong).Measuring input biasShorting the non-inverting input to ground through a dmm: less than 0.1uA, too small for my equipment to read.Measuring the voltage across a 1M resistor between the non-inverting input and ground: around 8-9mV. It does appear to slightly increase when I heat the part.Operating voltageSeems to work fine down at 5V (+-2.5), no changes in output waveform or input bias (if clipping is avoided).ConclusionsIt's a3554 opamp.

author: Whales
author_rank: Super Contributor
timestamp: September 07, 2019, 11:50:29 pm
content: Well that's a bit annoying. Looks like I'll need to order some from a more reputable supplier, may as well branch out a bit more then too.Now to try some more decapping...

author: Whales
author_rank: Super Contributor
timestamp: September 08, 2019, 01:12:26 am
content: Boiling-colophony (rosin) decapping has failed me. Lots of smoke and smell, no dissolution, not even enough to remove the part number. I think my heatgun is too cold. Might leave my next attempt to another day.

author: magic
author_rank: Super Contributor
timestamp: September 08, 2019, 06:03:24 am
content: Boiling rosin? I have heard about it but never done it. IIRC it needs to really be heated to boiling and kept boiling for minutes.Definitely start with cutting or breaking-off majority of the package, leaving only a small piece of epoxy around the die.IIRC this crap dissolves metal too. Not a problem for most of the chip, though, as it is covered with a layer of glass.Flames and electric heaters work toohttps://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/

author: Whales
author_rank: Super Contributor
timestamp: September 08, 2019, 10:51:15 am
content: Quote from: magic on September 08, 2019, 06:03:24 amYeah, I pre-snipped most of the chip away and ran for about 20 minutes. Some boiling occurred around the chip (I think it might have dissolved a bit of the leads) but it was mostly just smoke and smell. I think the smoke mainly came from small amounts of rosin climbing the test tube walls and getting heated more than the main pool.Thanks for the link

author: StillTrying
author_rank: Super Contributor
timestamp: September 08, 2019, 11:17:12 am
content: Quote from: Whales on September 07, 2019, 11:41:18 pmGoing by your 0-200k tests I make the current through the 0-200k 8-12nA, your 8-9mV across a 1M gives about the same value of ~10nA input bias current.QuoteJust use the Vpp down to 0.7 point. I usually find op amps can't make the data sheet's GBWP for outputs of 2-4Vpp but at a much lower 0.2Vpp output they can exceed it a bit.ConclusionsLM324

author: magic
author_rank: Super Contributor
timestamp: September 08, 2019, 11:32:19 am
content: I have never boiled rosin but I presume that boiling means boiling, bubbles of rosin vapor coming from the whole volume of the liquid.Bubbles around metal bits may have been hydrogen or some other crap if a reaction took place.

author: Whales
author_rank: Super Contributor
timestamp: September 09, 2019, 02:25:37 am
content: You are probably right about boiling vs hydrogen generation.Sidenote: the crossover distortion of these LM324s is particularly annoying. When cascading the opamps and operating near/in the crossover region their output seems to pick up all sorts of interference (probably because it's going high impedance). It took me a while to realise that was the cause and throw another resistor in.

author: magic
author_rank: Super Contributor
timestamp: September 09, 2019, 05:19:32 am
content: I have a question though:Increasing input impedance at IN+ makes the output godown. This looks like the input bias current is flowing into the pin rather than out of it.It should be the other way around in an LM324, the bias current should flow out of the pin due to PNP inputs.

author: mikerj
author_rank: Super Contributor
timestamp: September 09, 2019, 08:13:18 am
content: Quote from: Whales on September 09, 2019, 02:25:37 amYou can work around this by adding a pull-up (or pull-down) resistor on the output to bias it into Class A operation. Obviously this increases quiescent current and limits drive capability before the distortion returns, but for driving high-ish impedance loads it can work. That said, the best solution is to place them in the round filing cabinet.

author: Whales
author_rank: Super Contributor
timestamp: September 09, 2019, 10:04:41 am
content: Yeah, that's what I meant by throwing a resistor on. Indeed it only helpssometimes.Another realisation: a few years ago I tried using one of these "TL074"s to drive a discrete AB push/pull pair. No matter how I tried to bias things there was still crossover distortion (or I blew the parts up from creative arrangements or over-biasing). Doh!I'm not going to throw them out. Not only do I want to keep them for the opportune moment when a friend asks for a better opamp () but they're also the only non-single opamp I have left at the moment. I'll deal with the audio distortion until some more parts arrive.

author: xavier60
author_rank: Super Contributor
timestamp: September 09, 2019, 10:27:34 am
content: The counterfeiters apply surface texturing to the top of ICs after the original markings are ground off. But the dimple also gets textured which usually should be shinny.

author: StillTrying
author_rank: Super Contributor
timestamp: September 09, 2019, 12:57:11 pm
content: Quote from: magic on September 09, 2019, 05:19:32 amI think you're right,for the input voltage offset being corrected with increasing resistance the bias current would have to be flowing in,andthe measured 9mV across the 1M would have to be -9mV.

author: Whales
author_rank: Super Contributor
timestamp: September 09, 2019, 10:42:14 pm
content: I don't think I bothered checking the sign of the 9mV - it was a measurement just to see the effects of temperature.

author: Whales
author_rank: Super Contributor
timestamp: September 10, 2019, 08:42:58 am
content: These are the best die shots I can get of one of the fake TL074CN using the equipment I have at hand. Standard handheld optical zoom camera + a random half-convex lens.In the lower-right it looks like some black epoxy is still covering some pads.To decap: I used a cyclic heating and cooling technique. Heat the chip with a pencil torch until it starts to glow and burn, then quickly dunk it in cold water. Repeat several times. Eventually the black expoxy becomes very weak and you can gently crush it into powder using a pair of pliers.This beats having to completely incinerate the epoxy (it stinks like blown opamp for some reason) and it's reasonably quick (took me about 5 minutes). Most of the hard work is finding which piece of epoxy debris contains the die afterwards.I might see if I can get access to some microscopes at my uni. Otherwise: I'm happy to mail a couple of these dies to anyone who is interested or can offer better photos

author: magic
author_rank: Super Contributor
timestamp: September 10, 2019, 09:37:46 am
content: By the way, I clicked your DIY diodes project. I'm afraid that forward conduction involves some electrolysis, so the diode will have finite lifespan due to material loss even if it's protected from water evaporation.

author: Whales
author_rank: Super Contributor
timestamp: September 10, 2019, 11:41:32 am
content: Yes, the water electrolyses at the terminals. I think this electrolysis (namely the O2 generated) interacts with the sodium bicarbonate buffer, making it difficult to modulate the conductivity of these devices. I ended up doing my (undergrad) thesis on trying to find ways they could potentially be modified to create transistor-like devices.I should upload that report somewhere. There's some nice pictures of the al-bicarb glow (of which I've only been able to findone other photo ofon the internet, and only showing green). Also lots of pages of me complaining about various published works claiming they have made "transistors" but said devices appear to be useless for amplification (ie they can only variably attenuate, albeit many papers papers fail to prove eventhat).Thanks for having a look at my page, magic.

author: macboy
author_rank: Super Contributor
timestamp: September 10, 2019, 01:23:36 pm
content: Beware that TL072 and similar suffer from something calledphase reversalwhen the outputs swing too close to the negative supply rail. This perfectly explains the odd behavior seen in the original post.Google "TL072 phase reversal" and read.This highlights the need to read and understand specifications (and the application notes section) in the datasheet of any device used. This phase reversal phenomenon is not a secret and you would have been warned within the datasheet. That should have caused you to either keep the inputs well away from the rails (because this isnotan RR opamp, nor a single-supply opamp) or to choose a more appropriate device. The common LM358 can handle inputs right down to the negative rail.

author: magic
author_rank: Super Contributor
timestamp: September 10, 2019, 04:41:04 pm
content: The schematic shows ±6V rails and ground-referenced signal, there shouldn't be a problem.Quote from: Whales on September 10, 2019, 11:41:32 amTruth be told, I have no idea how one would even begin to electrically modulate conductivity of an electrolyte. But that's because I'm quite clueless about electrochemistryI found your "home-made diodes" link intriguing. I remember a few years ago somebody in America built working semiconductor transistors at home, hydrofluoric acid and all the fun stuff included.

author: Whales
author_rank: Super Contributor
timestamp: September 10, 2019, 09:00:53 pm
content: Quote from: macboy on September 10, 2019, 01:23:36 pmNothing is near the negative supply rail, have a look at the schematic and text in the first post. Ground = 0V, supply = +/- 6V.

author: Whales
author_rank: Super Contributor
timestamp: September 11, 2019, 04:29:22 am
content: I was melting at the fingertips whilst using this microscope. It's a beautiful piece of equipment -- a big thankyou to the people who let me use it.Logo and text:Full die:I tried to remove the large hunk of epoxy in the lower-right, however all I succeeded at doing was gouging out large areas of the die. Hopefully no text is hiding underneath it.

author: exe
author_rank: Unknown
timestamp: September 11, 2019, 05:36:20 am
content: I'm not an expert, but to me it looks like lm324:https://s.zeptobars.com/TI-LM324-HD.jpg.. I sort of see bjt long-tail pair at the input, so it's not a j-fet opamp. However, I dunno what jfets look like on IC. May be like those weird crosses here:https://zeptobars.com/en/read/ST-TL072-JFET-dual-opamp?

author: magic
author_rank: Super Contributor
timestamp: September 11, 2019, 06:21:11 am
content: Yes, it's more or less the same chip.The input is a differential pair of PNP Darlingtons. The input transistor of each pair is right next to the bonding pad and its emitter is connected to the base of the second transistor located towards the center of the chip. The latter have their emitters tied together and fed from one of those multi-collector PNPs near the central axis. Other collectors also feed emitters of the input PNPs to bias them in class A. Next up is an NPN current mirror, combined with those inverting PNPs that are some kind of LM358 idiosyncrasy, look up the schematic.The output is an NPN Darlington plus a PNP, without biasing. The rest is probably equivalent to the bizarre gain stage of the LM358 whose schematic can be found on the Internet if you care (look for full schematics, most of the time simplified is shown). Somewhere there is also hidden the 50µA output current sink.The big floods of metal are compensation capacitors, that's always helpful in trying to figure out opamp circuits. The transistors between the capacitors and output pads are the final transistors of the internal gain stage which drive the output stage. They also operate in class A, collectors are loaded by another multi-collector PNP in the center.

author: iMo
author_rank: Super Contributor
timestamp: September 11, 2019, 08:34:27 am
content: The TL06/7/8x series die shots are easy to recognize based on the input jfets, which are made in the form of an "X"

author: Zero999
author_rank: Super Contributor
timestamp: September 11, 2019, 02:25:14 pm
content: Quote from: magic on September 11, 2019, 06:21:11 amAre you talking about the LM358/324? If so, no, the input transistors are not Darlington pairs. They are emitter followers, driving a differential pair. The collectors are connected to the negative rail, not the collectors of the differential pair, so they're emitter followers.

author: magic
author_rank: Super Contributor
timestamp: November 05, 2019, 11:59:12 am
content: And... I found a dual version of this opamp.Crap quality because the image was take with household itemsBut it's quite obvious it's the same circuit and the same logo. Kinda looks like letters GLX to me, probably some obscure Chinese jellybean vendor who made this die.A keen observer will notice that right channel bonding pads look differently than all the others. That's because the opamp was bonded as a single channel one and sold as OP-07Clearly the counterfeiters are increasing sophistication of their operations, now being able to special-order a different pinout or perhaps buy bare dies and package them themselves. I wonder how long till somebody makes a dedicated half-358 opamp just for this purpose.

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 05, 2019, 01:03:23 pm
content: I think the text is actually up-side-down. And then it says 971. So could that be a (wannabe) TL971 or TS971?

author: magic
author_rank: Super Contributor
timestamp: November 05, 2019, 01:26:47 pm
content: And the dual says 956. These numbers have to be something else.The topology is clearly LM358/324. It isn't rail to rail, the outputs are emitter followers and the input has two diode drops in series with it.

author: Whales
author_rank: Super Contributor
timestamp: November 06, 2019, 10:57:32 am
content: Quote from: magic on November 05, 2019, 11:59:12 amThats a really good photo if you're only using household items. I suspect you're using a standard biology microscope of some sort? The lack of chromatic aberration says you are using some form of reasonable/coated lens.QuoteWait, floating inputs. Do you have any spares? Tie the known inputs somewhere safe, scope the power suppy current draw and "tap" the chip (on the epoxy) with your fingerCould be a new detection techniqueQuoteSidenote: The fab people could be separate to the packaging people who could be separate to the marking people (who arelikelyseparate from the sales people you got the chip from). The OEM of the chip (shall we call them GLX for now?) could be completely legit & doing nothing wrong.

author: magic
author_rank: Super Contributor
timestamp: November 06, 2019, 04:44:20 pm
content: It was a webcam lens stacked onto the fixed lens of a 1/3" sensor compact camera.The digicam needs to be tiny to get close to the webcam lens and see anything through it.The webcam lens needs to have relatively large diameter glass to reduce vignetting and diffraction.LED lighting from the side.

author: yunLad
author_rank: Newbie
timestamp: December 19, 2021, 03:54:38 pm
content: Made my first die shot!Not worth creating a new topic but I got burned on aliexpress recently, not expecting someone would counterfeit a cheap opamp like TL074. Turns out they were rebranded 324s (at least that what the die states - 324n24)Couldn't find this die anywhere on the internet so not sure about manufacturer.

author: magic
author_rank: Super Contributor
timestamp: December 19, 2021, 04:49:20 pm
content: Yeah, LM358/LM324/RC4558 is basically all you get ordering the cheapest opamps from Ali.A recently observed addition is the LM393 dual comparator.The die looks quite small, is it 1×0.75mm or so?That's another thing about those fake chips, they are distinctly smaller than products of big manufacturers (about 1.5×1.5mm for LM324).There have to be some unknown factories in China which specializing in making those miniaturized jellybean chips. Their products are so cheap that you will rarely even find recycled LM358 or similar on auction sites anymore.

author: yunLad
author_rank: Newbie
timestamp: December 19, 2021, 10:44:46 pm
content: Oh, forgot to mention the size. Absolutely tiny, 0.9×0.7mm.Decided to decap LM324s (that seem to behave up to spec) and it turns out they are different too... Found a more fitting thread so I posted them therehttps://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/msg3884651/#msg3884651

author: Cerebus
author_rank: Super Contributor
timestamp: December 20, 2021, 02:57:29 am
content: Quote from: Audioguru again on September 06, 2019, 12:21:02 pmOh lordy, not this rubbish again.Yes, the LM324/LM358 makes a lousy audio amplifier but just because it's lousy for audio isn't an excuse to misrepresent its actual parameters at every opportunity you're given to bring it up. You literally do this in every thread you spot where someone mentions the LM324 or LM358.Just to prove a point, here's Bode plots of an actual genuine ST LM358 (the dual version of the LM324) and an actual genuine Texas TL072C pulled out of the parts draws a few minutes ago. Both configured for a gain of +1 and tested with a 1V signal.:As one can see the TL072 has a slightly higher 3dB point but at 100kHz they are both quite happy, whereas according to you the LM358 should have run out of steam at a "few kHz" but it hasn't. As far as slew rate is concerned the TL072 is far superior, but both will happily pass a 2V ptp signal at 100kHz.

author: magic
author_rank: Super Contributor
timestamp: December 20, 2021, 08:15:50 am
content: Quote from: Cerebus on December 20, 2021, 02:57:29 amThat's the point he was trying to make.

author: Cerebus
author_rank: Super Contributor
timestamp: December 20, 2021, 02:15:22 pm
content: Quote from: magic on December 20, 2021, 08:15:50 amNo, he has consistently claimed that the LM358 family don't go above 2 kHz or so, try a Google site search for "site:www.eevblog.com/forum audioguru LM324" or "site:www.eevblog.com/forum audioguru LM358". He has an obsession with it and a mission to proselytise his ignorance.

author: magic
author_rank: Super Contributor
timestamp: December 20, 2021, 03:33:16 pm
content: Well, it will fall apart if you want to have any sort of closed loop gain or output amplitude. GBW and SR just aren't its strength.There are reasons why cheap DIY audio projects use TL072 instead of LM358

author: Cerebus
author_rank: Super Contributor
timestamp: December 20, 2021, 05:25:19 pm
content: Quote from: magic on December 20, 2021, 03:33:16 pmAnd no-one is disputing that, just the spurious claim that it only works to "a few kHz". LM358 GBW 1.2MHz, 0.6 V/us, TL072 3MHz, 5V/us - neither are stellar performers.

author: magic
author_rank: Super Contributor
timestamp: December 20, 2021, 06:19:22 pm
content: LM324/358 and µA741 have a particular reputation of being "too slow for audio" because they barely deliver a few V RMS above 10kHz, so I suppose he was just repeating that meme.And FYI, Audioguru hasn't posted here for over a year so I wouldn't waste much time debating him

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2021, 08:44:00 am
content: Quote from: magic on December 20, 2021, 06:19:22 pmIt's also not true. In an audio signal, the large swings are due to bass frequencies, so the slew rate is not normally an issue. The relatively high noise and crossover distortion of the LM358, although the latter can be fixed by adding a resistor to the output.