LM386 Amp: fake chips? - Page 1
Forum section: electronics / projects

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 23, 2021, 11:29:03 pm
content: Hello EEVbloggers,Being a beginner in making circuits, I would need an expert's opinion on an issue I am having with an LM386 amplifier.I am building a simple audio amplifier based on the venerable LM386, just for fun. I wanted to listen to the output of an oscillator that I am also building. Thus, I have built the following circuit on a breadboard, using Panasonic film and electrolytic capacitors, in addition to a (supposedly) NI LM386 chip bought on Amazon.Below is the schematic of the circuit:Simulating this circuit with LTSpice I get the output I would expect according to the specs: with 9V supply and 8 Ohm load, a 6V peak-to-peak sinusoid output for a 0.300V peak-to-peak, 1KHz, input, i.e. a gain of 20. The spice model is unofficial, but it does perform according to specs, at least for what I need.When I provide the same 0.3Vpp input (from a function generator) to the breadboarded circuit I get an approximately 1.6V output peak-to-peak on an 8 Ohm load. When there is no load connected, the output signal is about 5V peak-to-peak. If I increase the amplitude of the input signal even a little the output clips and distorts on the positive peaks. So, it seems like this chip has a maximum gain of about 5, not 20, with an 8 Ohm load. The supply is 9V, like in the simulation, provided by a bench power supply.I have double and triple checked all the connections on the breadboard and the values of the components. I cannot figure out whether I am missing something obvious (entirely possible) or whether I just lost the chip lottery and got some counterfeited parts. I have ordered another batch of Ti LM386 from DigiKey (not delivered yet) to make a comparison.The markings on the chips from Amazon seem to be from NI but the logo is a little faded and fuzzy. I do not have a verified original to compare to, however.Any suggestions?Thanks in advance.

author: wraper
author_rank: Unknown
timestamp: January 23, 2021, 11:38:46 pm
content: QuoteDo you mean National semi? Chances of receiving fake crap from amazon 3rd party sellers or ebay are extremely high.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 24, 2021, 12:35:13 am
content: Quote from: wraper on January 23, 2021, 11:38:46 pmYes, it is supposedly from National Semiconductors (sorry for the typo, I will fix it in the post). I am afraid you are right, but before jumping to conclusions I wanted the opinion of people who have been around EE design longer than me.

author: wraper
author_rank: Unknown
timestamp: January 24, 2021, 12:59:58 am
content: Well, you could connect in- directly to GND, although I don't think it will change anything. Capacitor is not needed there. You could try increasing gain by adding capacitor between gain terminals and see how it affects output swing. Did you use DC blocking capacitor between signal gen and amplifier input? Also it's not clear if signal gen provided only positive signal, or swinging from negative to positive voltage.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 24, 2021, 03:09:19 am
content: Quote from: wraper on January 24, 2021, 12:59:58 amThanks for the suggestions.I have tried higher gain (namely 200 with a capacitor between pin 1 and 8 ), but, as expected, it distorts even worse. With a load, the output cannot exceed a couple of volts peak to peak no matter what I do.I have used a decoupling capacitor in input and the generator does +/- amplitude, so when set to 0.3Vpp it does -0.15V to +015V.I tried also connecting pin 2 directly to ground, but as you said, it made no visible difference.

author: floobydust
author_rank: Super Contributor
timestamp: January 25, 2021, 03:05:16 am
content: There are a few traps with the LM386 to first check for, before blaming the IC. Especially on a breadboard. It can go unstable at higher output power, which is confusing because it all works at low power but misbehaves (distorts).The circuit needs single-point grounding, especially the loudspeaker(-) return should go the power(-). Breadboard bus strips at higher currents are not ideal and the small voltage drop across them gets amplified.The usual LM386 fiasco is due to the part oscillating around 12MHz during the bottom sine-wave excursion called "bottom-side fuzzies". It will sound like distortion and if your scope is slow looking at 1kHz sine wave, 12MHz can be hard to notice but it's there.So you need low impedance like 1uF to 2.2uF ceramic caps across power right at the IC, as well as the usual 100uF bulk capacitance to prevent motorboating. The output Zobel or ferrite bead never seemed to help much at the output side. The speaker wires become a RF antenna transmitting 12MHz which is why everything just goes off the rails.The IC also loves to amplify RF, AM radio coming in, so an RC filter is mandatory for pin 3.C1 47pF with no R ahead of it is not ideal. I use 1k/1000pF (159kHz) rolloff would not affect treble.The scope should be DC-coupled and Vout idles around 1/2Vcc if the IC is not damaged or in case your output coupling cap is not in backwards or shorted.Check your signal generator does not have a small DC offset, or lop-sided waveform that would look like a DC offset. The LM386 (+)input best with a coupling capacitor 0.22uF to the input to prevent hassles, the (-) input is fine grounded.

author: magic
author_rank: Super Contributor
timestamp: January 25, 2021, 09:06:09 am
content: I wouldn't be surprised if there are fakes with reduced output current capability.I once bought a pair of those figuring they may come in handy, but never really used them for anything because they frankly suck, IMVHO at leastSo I tore one of them down and the die inside was very tiny, like those in fake opamps from China. But it wasn't any generic opamp like LM358, clearly something else with very few small signal transistors and "big" outputs. But it was still a tiny die so not that big in the grand scheme of things. Less than 1mm² die area, I would say.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 25, 2021, 03:14:11 pm
content: Quote from: floobydust on January 25, 2021, 03:05:16 amThanks for all the tips: I will try them and post the results. I do have a decoupling cap in the +In pin, so it should not be a DC issue. I also did what I could to make all the return GND paths into the same spot (pin 4). I will post some pictures of the updated schematic and of the breadboard later. I am positive that none of the polarized capacitors are backward and the scope is DC coupled.So, that leaves the issue of oscillation: I will add the input RC filter and see what happens; I will also positively verify whether the 12 MHz oscillation is there. I have looked at the FFT of the output and did not see a spike at 12 MHz, but will verify again, for good measure.Thanks again to all who replied. If there is interest in seeing how it goes, I will continue to update the post. It may be useful to others going down the same path.

author: floobydust
author_rank: Super Contributor
timestamp: January 25, 2021, 09:40:57 pm
content: For $1.50 I've ordered those cheapola LM386 amplifier kits, Digi-Key charges $1.83 just for the IC alone- never mind pc board, potentiometer, DC jack etc. Unbelievably cheap.But... the IC that comes with it is the usual alien laser marking and I imagine they've done a die shrink. It works as the original NS does, for ones I have.The output stage PNP is the hassle (-ve swing) I think. Have to send the IC to Noopy for analysis if it turns out to not meet specs.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 03:48:56 am
content: Here are some results of the latest tests with the modifications suggested so far. In the pictures below, the blue trace is the input, the yellow one is the output. I added also a Capacitor and VR between Pin 1 and Pin 8 (not shown in the LTspice schematic); the VR has been adjusted to give minimum gain (for very low distortion) to maximum gain (high distortion). The output of my LM386 cannot exceed 3Vpp with the 8Ohm load, whereas the datasheet and simulations predict it should be 6Vpp.1. Simulated circuit with LTSpice2. Measured: maximum output without distortion for 1KHz Input, 300mVpp3. Measured: maximum output with distortion, same input as above.4. Picture of the breadboardMeasurement System:Analog Discovery 2, with BNC adaptor and shielded probes.Supply: +9V DCThe maximum FFT range for this scope is 400kHz so I cannot tell whether there is a 12MHz oscillation. I have, however, implemented an input RC filter and added the recommended capacitors to prevent such oscillation.If anyone can suggest some other worthwhile measurement, I will try it if I can. At this point, I am fairly convinced that the chips do not meet specifications and are likely counterfeit. I have, of course, tried several chips from the same batch. As soon as the parts from Digikey arrive I will post an update.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 03:55:22 am
content: Quote from: floobydust on January 25, 2021, 09:40:57 pmThat is probably a wise approach. I am trying to learn Electronics, so it makes sense for me to explore a little more. Fortunately, this is just a hobby project, so spending a few dollars to get reputable parts is not going to break the bank for me.What is noopy?

author: floobydust
author_rank: Super Contributor
timestamp: January 26, 2021, 05:50:58 am
content: I don't see any LM386 HF oscillation in those scope traces.Are you using a 9V battery for power? It could be sagging under load. Maybe scope power too.To be clear, the input RC filter just attenuates RF/AM radio from getting into the LM386. Stuff way above the audio band. The bottom-side fuzzies are mainly the Vs bypass cap and 10R 0.1uF network and grounding that can set that off.EEVblog member Noopy does die shots (pictures) in many threads here on EEVblog, I've sent him IC's to de-encapsulate, great to ID fakes.Opamps - Die picturesSome 555-Timer-DiesLM723 die picturesTransistors - die picturesLogic-ICs - die pictures

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 03:49:14 pm
content: Quote from: floobydust on January 26, 2021, 05:50:58 amThe data I have shown was captured with the board powered with a BK Precision bench power supply set to +9V, drawing about 50mA according to the power supply display.The AD2 scope was being also supplied with a 5V DC 2A power supply, as recommended by the manufacturer, I have used probes set to 10x attenuation for the measurements (and set to 10x on the scope software too).I may send a couple of chips to Noopy too then. It looks interesting if he would care to look into the matter.Thank you again for your help and to the other members who contributed.

author: rstofer
author_rank: Super Contributor
timestamp: January 26, 2021, 09:16:22 pm
content: That scope shot sure looks like you're running out of voltage.Have you calculated the power? It is pretty limited so your gain may need to be reduced.Spend some quality time with the graphs in the datasheet and see if they give a clue.There are different dash numbers and they have different characteristics.https://www.ti.com/lit/ds/symlink/lm386.pdfLook at Figure 6 and see what happens to THD when the output power gets above 200 mWOn the first page, under Features, it discusses THD in terms of a 125 mW output and this is where you probably want to work.For 125 mW, the maximum output voltage with an 8 Ohm load is 2.828Vp-pand with a gain of 20, the maximum input voltage is 0.14Vp-por 140 mVhttps://www.random-science-tools.com/electronics/dBm-Watts-volts.htm

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 09:26:04 pm
content: Quote from: rstofer on January 26, 2021, 09:16:22 pmExcuse my ignorance on the topic, but in what sense is the scope running out of voltage? The AD2 is rated for +/- 20V, and I am using a 10x probe that would bring the range to +/- 200V. I am also using an external power supply for the scope, as recommended by Digilent. The output of the LM386 is distorting above about 1.5 V. I have measured much higher voltage signals with that scope without any problem. I can show you a 20V signal from a Wien Bridge oscillator with a TL072 Op Amp, with very low THD measured with the same tools.Here is the datasheet for the LM386, in case it is useful to reveal the issue(s):https://www.jameco.com/Jameco/Products/ProdDS/839826.pdfThe way I read the top-right figure on page 4 is that with an 8 Ohm load, the expected max swing should be 6Vpp. Am I missing something critical or silly?The center bottom chart indicates that the output power should be around 400mW with a 9V supply on an 8 Ohm load, maximum output power being 700mW. The device I am looking into does not seem to exceed about 90mW. So your calculation is correct, but it is simply confirming the issue, right?

author: rstofer
author_rank: Super Contributor
timestamp: January 26, 2021, 09:42:15 pm
content: Quote from: cyb3rfly3r on January 26, 2021, 09:26:04 pmI didn't mean to imply the scope was running out of voltage, the chip output is banging up against the power supply rails. That's why the tips are flat.The AD2 is a wonderful tool for this application. Instead of dialing up 10X, I bought a pair of fixed probes, no switch. Like you, I want to protect the AD2.I revised my reply considerably. Among other things the power calculation was wrong. That's what happens when I hit Post with my head up and locked.Crank down on the gain or reduce the input signal. You are driving the power amplifier well into the high THD region.I think...QuoteYes, that graph says the chip won't leak smoke at those values. But it doesn't mean the output won't be severely distorted. Look at the Distortion vs Output Power graph. Rated 0.2% distortion is at 125 mW on first page under Features.Data sheets are interesting...

author: drussell
author_rank: Super Contributor
timestamp: January 26, 2021, 09:51:11 pm
content: Quote from: cyb3rfly3r on January 26, 2021, 09:26:04 pmI believerstofermeans that your LM386 circuit is running out of voltage headroom, not that the "scope" is running out of measuring range or something....You do see figure 6, where the distortion goes wild above about 200 mW typical output, right? I think you may be expecting far more clean output power than most versions of a 386 can deliver.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 09:52:36 pm
content: Quote from: rstofer on January 26, 2021, 09:42:15 pmOh, ok I see what you meant now. Sure, it is hitting some limit, but it should not be the rail, it is being supplied with +9V from a benchtop supply, not a depleted battery. This distortion is out of spec, which is why I suspect it may be a counterfeit chip. At this point, I am just curious to learn. I did lower the gain and the signal to obtain a clean signal, I can drive it with a 75mV signal at A=20, no problem. The specs say that the output should be a lot more capable so I was wondering what had I done wrong. I will confirm the diagnosis with Ti chips from DigiKey in the next few days.Thanks for your comments.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 09:59:26 pm
content: Quote from: drussell on January 26, 2021, 09:51:11 pmWell, this is one area in which I definitely would trust the experts: if the specs from National Semiconductor and/or TI are too rosy, then I can live with that.I am just wondering why what I see on my measurements and the specifications do not match. The spec says that with a 9V supply,8 Ohm load, the average power output should be 400mW at below 10% THD. That should still be a clean sine wave, right? The maximum drive should be able to go all the way to 700mW, 10% THD in theory. I am seeing about 100mW max before clipping heavily, it seems that it should be able to output a clean output at that power level. I have varied the gain very gradually with a pot and the distortion sets in gradually, but the output never exceeds about 2Vpp.If I am misreading the specs or measuring incorrectly, I would definitely would like to know, before bad habits take hold and ruin a more important project. Thanks!

author: rstofer
author_rank: Super Contributor
timestamp: January 26, 2021, 10:02:40 pm
content: uA741 op amps were supplied with +-15V supplies but the usual signal swing was limited to +-10V in the analog computing world. There was a need for quite a bit of headroom with these old devices.That you could get an acceptable output by cranking back on the input shows that the chip has limits and if you want clean audio, you can't have maximum power.I doubt the TI chips will be any different. I never buy floor sweepings, I have enough problems getting things to work. All of my components come from DigiKey or Mouser, sometimes Newark.

author: floobydust
author_rank: Super Contributor
timestamp: January 26, 2021, 10:31:09 pm
content: The LM386 output stage is lop-sided (EF on top,Sziklaion bottom) so it's output voltage loss is not symmetrical. I would be curious what the output waveform looks like just at the onset of clipping. I thought the +ve portion is where most of the voltage is lost, yet OP seems to get symmetrical clipping

author: drussell
author_rank: Super Contributor
timestamp: January 26, 2021, 10:33:13 pm
content: The OP still has not even told us what variant of 386 this is, even if they are "genuine parts."The various variants like -1, -3 and -4 have significantly different capabilities....

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 10:55:09 pm
content: Quote from: drussell on January 26, 2021, 10:33:13 pmTrue and sorry for the omission. It is a National Semiconductors LM386N-4, according to the markings on the part.

author: magic
author_rank: Super Contributor
timestamp: January 26, 2021, 11:00:58 pm
content: Do some tests at DC. Pull one input up so that the output hits the rail. See how close it gets to the rail. Load it with various resistors to the opposite rail. See how much current it can deliver. Try not to overheatCan you post a closeup of the suspected chip?

author: drussell
author_rank: Super Contributor
timestamp: January 26, 2021, 11:14:19 pm
content: Quote from: magic on January 26, 2021, 11:00:58 pmIndeed...Check your necessary headroom to the rails. A 9v supply is probably pretty low to try to get enough total voltage swing for an 8Ω load on a -4 chip. Does it work properly at 12-15 volts?

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 26, 2021, 11:33:30 pm
content: Quote from: drussell on January 26, 2021, 11:14:19 pmI will do these tests and post results, including a closeup of the chip if my magnifier is enough (do not have a microscope yet).Thanks.

author: ve7xen
author_rank: Super Contributor
timestamp: January 26, 2021, 11:57:30 pm
content: Quote from: cyb3rfly3r on January 26, 2021, 09:59:26 pmNot really. 10% THD is very bad. A triangle wave is about 12% THD. So what you are showing I would reasonably think could be 10%.

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 27, 2021, 12:01:40 am
content: Quote from: ve7xen on January 26, 2021, 11:57:30 pmI see, good point. I do not have a good baseline for what 10% THD should be like.

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 12:06:13 am
content: Quote from: ve7xen on January 26, 2021, 11:57:30 pmAgreed. I wouldn't exactly call a "sine wave" at 10+% THD "clean."Driving your speaker with something which quickly approaches a square wave will certainly increase the average power output, which might be fine for a buzzer, horn, solenoid, motor, oscillator or something but isn't going to "sound" very good.edit:repair typos

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 12:15:18 am
content: Quote from: cyb3rfly3r on January 27, 2021, 12:01:40 amI think if you take a clean sine wave, then lop off the peaks completely flat across at 82.5% of each of the top and bottom of the wave height, that's about 10% THD from that clipping alone.

author: rstofer
author_rank: Super Contributor
timestamp: January 27, 2021, 12:39:55 am
content: Quote from: cyb3rfly3r on January 27, 2021, 12:01:40 amI don't know how to set it up but apparently the AD2 will measure and display THD vs Freqhttps://forum.digilentinc.com/topic/4918-can-i-measure-freq-vs-thd-with-network-analyzer/

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 12:44:43 am
content: I think 10% THD from clipping an otherwise perfect sinewave would look like this, right?Someone check my math though... I could be out to lunch... hahaIt's certainly not going tosoundlike a clean sinewave anymore.

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 03:37:18 am
content: I thought I would point out a couple things that I forgot to mention before, just for completeness...Quote from: cyb3rfly3r on January 26, 2021, 03:48:56 amFirstly, I think that most of those single-curve graphs in theNSandTIdatasheets are showing theTypical Performance Characteristicsfor the variant usually known as LM386-3.QuoteWhich variant did you happen to order from Digikey?The LM386-4 variant that you are trying to use is pretty much useless below about 5-6 volts supply voltage, regardless of what you're trying to drive. That is the main reason why there are the various different versions, so they can be optimized for their typical use case in small battery operated cheesy devices like those old wired $25 home intercom systems, kids toys with a squarewave tone generator or whatnot where they found widespread use back in the day.I don't have my old NS paper databooks from the 80s-90s here with me, but on the old original NS parts, the LM386-1 was optimized for typical 6 volt and the LM386-3 for 9 volt operation into the usual 3.2-8Ω load found in most typical devices and were rated for an absolute maximum 15V supply. The LM386-4 was the higher voltage variant, optimized for more like 12-18 volts with an absolute maximum of 22V and typically used loads more in the 8-32Ω range.You are trying to get full power out of the -4 variant which is the one designed for higher potential power output on higher supply voltages with higher impedance loads. The chip doesn't really work below 5-6 volts, so when you're trying to run on a (for the -4) low voltage of 9v, you don't have enough headroom to not clip severely on the voltage swings because the chip needs an extra 2-3 volt margin at the "top and bottom side" of the supply compared to the output voltage in order to actually work properly at any kind of useful total power level. Similarly to an old-school 7805 not being a modern LDO, the venerable old LM386 series is not a "rail to rail," "power" op-amp equivalent. There are several silicon diode voltage drops in "top" and "bottom" of the circuit. If I had my databooks here, I would check if there might be an equivalent schematic in there or at least they might have specified what variant those graphs published in the newer datasheets were with test circuit, etc. I don't recall, that was many moons ago...QuoteThe LM386-4s that you are using seems to be behaving as I would expect it to in this scenario and probably are genuine parts and operating within their specifications and typical operating parameters.You also need to remember that these are really intended as a 125-250mW output class devices into typical loads at tolerable distortion levels in most applications. Youcanpush them harder if you want within their thermal dissipation limits if your application is okay with that tradeoff, but distortion rises rapidly and you're also not going to get much optimal power transfer unless you have carefully matched your load impedance to the power supply voltage, etc. If you're using them for audio you really need to keep your expected power levels down to below something like 1% THD absolute maximum, not 10% THD, even for voice, if you expect it to not be trapezoid-shaped distorted fuzz that comes out instead of audio. These things really aren't intended for high fidelity music or anything in any case, though!QuoteYou can always "zoom in" on the regular oscilloscope rather than trying to find it on the FFT when looking for high frequency oscillations. The AD2 is 100 MS/s isn't it? You should easily be able to see any kind of HF or RF parasitic oscillations as you zoom in your timebase.edit:fix typos

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 27, 2021, 04:01:53 am
content: Firstly, many thanks again to all who suggested tests to do: I have learned a lot, including how to use the Network Analyzer of the AD2, which I had no idea could calculate THD out of the box. One caveat: it is the first time I use that feature of the AD2, so I hope I did not mess up the measurements.Picture of the chipBelow, I attached some pictures of some of the tests I did. This is a subset of all that is possible, but I think the picture is becoming a little clearer. My conclusions so far:- The output (before the output capacitor and Rload), with the maximum rated input of 0.4V on In+, sits at about 4.6V DC with a 9V supply, more or less as expected.- At a higher supply voltage, 12V to 15V, you do get a little more amplitude peak-to-peak with a clean output: I was able to get 6Vpp output with a pretty clean sine wave (see also THD of 0.63% at that supply voltage). Of course, the device gets hotter, so I would not use this chip at more than 12V normally.- Distortion sets in pretty abruptly once you go beyond 150mV Input with 9V supply or 250mV Input with the 15V supply. In that case, the THD is pretty bad, about 15% THD.So, I think I understand the limitations of this chip at this point. I am not sure whether it is original or not, because the last conundrum I cannot figure out is the specifications of the expected output Vpp on the datasheet, which still do not match with anything I measured (distorted or otherwise). Perhaps it is just a rosy advertisement, copied year after year from a lucky batch of chips made 30 years ago?

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 27, 2021, 04:11:43 am
content: Quote from: drussell on January 27, 2021, 03:37:18 amIn short my answers:- I ordered the same variant, LM386N-4 from Texas Instrument (should be exactly the same, as TI acquired N.S. at some point).- I am reaching the same conclusion: likely an original part, but the specifications could have been more clear about the intended use of each variant; thanks a lot for your perspective. That is precisely the kind of information that you can get only from experts.- The trace on the AD2 does show a little fuzz when I zoom-in, but I cannot tell what is normal, especially on a breadboard. I will experiment a little more on this point.Thanks so much!

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 04:23:07 am
content: Quote from: cyb3rfly3r on January 27, 2021, 04:01:53 amLearning is the whole point.I played with and learned from LM386 chippies too, it just happened to be 35 years ago.QuoteWell, that depends on what impedance of load you are driving. You need to start paying attention to things like which curve on which output impedance graph forDevice Dissipation vs Output Poweryou're looking at to design within the limits.The output impedance is missing and not specified in the current TI datasheet for figures 7, 8 and 9. They are for 4Ω, 8Ω and 16Ω loads, respectively. The somewhat older National Semiconductor one from 2000 or whatever it is, linked above, does label the graphs correctly but still seems to be an abridged version of the datasheet compared to what I recall from decades ago, but that could also just be me...

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 04:26:40 am
content: Quote from: cyb3rfly3r on January 27, 2021, 04:11:43 amIf you intend for your end device to operate from 9V then you want the appropriate LM386-3 variant.If you're just playing around and aren't intending to build a specific end device yet, then play away!

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 27, 2021, 04:38:00 am
content: Quote from: drussell on January 27, 2021, 04:26:40 amI am indeed just playing around. I will use this device at 12V if I need a clean output with an input of about 200mV. The focus on 9V was due to it seeming the optimal design point based on the device dissipation shown in the datasheet and the maximum (declared) output swing, which started the whole post.Since the datasheet does not specify which variant the curves are for, it makes sense that they are for the most popular variant, the LM386-3, as you say. I just wish they added the one sentence: "Curve shown for the LM386-3 variant, with the test circuit A on Page 3".

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 04:38:47 am
content: Quote from: cyb3rfly3r on January 27, 2021, 04:11:43 amWell, you do always kind of have to engineer these things to your given application, but sometimes you really have to look closely to see what they're talking about, especially when you have things like a whole family of chips.For example, notice that they only show up to 12V on the 4Ω graph as higher voltages are generally inappropriate on lower impedance loads with the higher supply voltage chip variants, whereas the 8Ω and 16Ω graphs have curves for running an LM386-4 on 18V.The more you get into electronics, the more time that you will find being spent trying to decipher the magic mythical code contained hidden deep within sacred datasheets and debugging your circuitry creations, trying to force them to operate somewhere between what the manufacturer intended and whatyouexpect or intend it to do!

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 27, 2021, 04:45:07 am
content: Quote from: drussell on January 27, 2021, 04:38:47 amI usually work with software, so I am getting into hobby electronics in the hope that the hardware guys are better at documentation

author: drussell
author_rank: Super Contributor
timestamp: January 27, 2021, 05:22:34 am
content: Quote from: cyb3rfly3r on January 27, 2021, 04:45:07 amWell at least with hardware, some kind of documentation at least existed at some point, although actuallyfindingit can be another matter entirely. Most of the time with software it seems that there is no documentation other than the code itself.Pretty much everything you need to know about the variants isalludedto in the typical operating conditions electrical characteristics chart at the beginning of the datasheet but the nuances of something like that is not exactly going to be obvious if you've never used them before:

author: cyb3rfly3r
author_rank: Contributor
timestamp: January 31, 2021, 05:58:26 pm
content: Hi all,Posting the final update on this post, since I have received the TI LM386N-4 chips mentioned earlier. After some tests, the newer chips from DigiKey perform practically the same as the ones I had from National Semi. The newer TI version distorts a little less, but not a significant result. The output is clean to about 250mV input, giving about 4.0Vpp output with the +15V supply.I connected my Wien Bridge Oscillator and, after adjusting the level to about 200mV input, I got a nice output and clean-sounding ~440Hz output.Harmonics of the input are below -60dB level and about -44dB output, which is fine. The LM386 does not seem to be adding distortion, just amplification of what is being input.At this point, I feel the topic is concluded. Thanks to all who helped me get here.