Anyone know the difference between LM386N -1 and -3 - Page 1
Forum section: electronics / projects

author: TimNJ
author_rank: Super Contributor
timestamp: September 02, 2018, 03:03:23 am
content: Hi all,I'm in the middle of writing up some of my old projects for my website, and I ran into an old question that ultimately I never found an answer to..The LM386 is a pretty horrid chip by most accounts, but I am still curious nonetheless.Once upon a time, I built a small guitar amp with an LM386. I used the LM386N-3because the table in the TI/National spec sheet said it was the higher power part (700mW @ 9V vs. 325mw @6V). But, in reality, if you look at the 8-ohm device dissipation vs output power curves, you'll see that the rated power specs just seem to be referring to a single family of curves.Does anyone know the deal with the different variants, specifically between -1 and -3?Perhaps the devices that perform better at higher output powers get the -3 suffix and those which do worse (higher THD?) get the -1 suffix?Thanks.

author: t1d
author_rank: Super Contributor
timestamp: September 02, 2018, 03:23:48 am
content: Go to Mouser.com. Select the general item, that you want to compare... LM386. Once that sort it made, check the models, that you want to compare. It will look like this, but you will get more information, than what I clipped. Try to match footprints, etc., which I did not, because that makes a difference, to specifications, sometimes.

author: TimNJ
author_rank: Super Contributor
timestamp: September 02, 2018, 03:32:59 am
content: Thanks. I'm very familiar with Mouser.I am mainly asking about TI datasheet and the lack of any real distinction between the -1 and -3 variant. They say the -3 variant is a higher power part, butof courseyou're going to get more power out of it if you use a higher supply voltage.That's why I'm wondering if the power rating is more of a suggestion based on measured performance at the factory.

author: floobydust
author_rank: Super Contributor
timestamp: September 02, 2018, 04:45:47 am
content: I thought the different power offerings were optimized for class AB bias current depending on Vcc for the number of batteries.This was for best quiescent current drain in battery-powered applications. So the output stage bias current is suited for Vcc of 6, 9, 12, 18V. The -2 might have been for 4.5V or 5V? The -4 runs to higher Vcc of 5-18V verses -1 and -3 at 4-12V.TI today has a hack job butchered version of National Semi's datasheet for theLM386.[url=http://[url=https://www.njr.com/search/search.php?part=lm386&x=0&y=0]NJR][url=https://www.njr.com/search/search.php?part=lm386&x=0&y=0]NJRhas better datasheets but for -3 and -4 only.I dislike the LM386. High distortion, noise and loves to oscillate at RF. It's the worst sounding chip amp, ever. You don't even need a fuzz box lol.

author: TimNJ
author_rank: Super Contributor
timestamp: September 02, 2018, 05:40:38 am
content: Quote from: floobydust on September 02, 2018, 04:45:47 amAh that sounds like a probable answer. The NJR datasheet shows a current mirror with the reference current dependent on the supply voltage...so that makes sense. To me, it sounds like youcoulduse the -1 variety @ 12V but the bias network would chew up more current. Maybe something like that?Trust me, I don't love the LM386 either. But, when I didn't know any better, it seemed like a fun little chip.Thanks.

author: Audioguru
author_rank: Super Contributor
timestamp: September 02, 2018, 12:19:47 pm
content: The LM386 works best with a supply that is 6V to 9V. At 12V, the output power is increased only 17% more than at 9V but the heating is 60% more. Its heating is awful when the speaker is 4 ohms.With a 9V supply and an 8 ohm speaker the LM386 clips at 0.45W and sounds fine below clipping if the anti-oscillation parts (the RC Zobel network at the output to ground) are added. I prefer the LM390 that has bootstrapping and a 14 pins DIL package for higher more efficient output power but it is not made anymore.

author: TimNJ
author_rank: Super Contributor
timestamp: September 02, 2018, 04:06:20 pm
content: Quote from: Audioguru on September 02, 2018, 12:19:47 pmThat's true for an 8-ohm speaker. You can get a little more power out of it with a 16-ohm speaker and 12-16V supply.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 02, 2018, 05:53:57 pm
content: I gave it up with the LM386; instead I use the TDA7052 which has from my point view a lot of advantages

author: bloguetronica
author_rank: Frequent Contributor
timestamp: September 02, 2018, 08:28:50 pm
content: Hi,The data sheet seems to suggest that the main difference is the dissipated power, being the "-3" version rated for 700mW, and the "-1" version for just 325mW. I was going to suggest that you could use something like the TDA2003, that is better sounding IMHO. Ironically, despite being better sounding and about the same age, the TDA2003 is not made any more. I also tried to see if there were pin compatible alternatives, to no avail.Quote from: Audioguru on September 02, 2018, 12:19:47 pmOn one hand 0.8W maximum dissipation (as per the data sheet) is not a big deal, even for a DIP-8 package. I would be more concerned about THD and the lack of delivered power. I can say that I've built a kit with this chip, and the dissipated power was the least of my concerns.Kind regards, Samuel Lourenço

author: TimNJ
author_rank: Super Contributor
timestamp: September 03, 2018, 03:26:50 am
content: Quote from: bloguetronica on September 02, 2018, 08:28:50 pmThanks. Yes one is rated for 700mW and the other is rated for 325mW but there’s very little insight into why you would choose one over the other.Both -1 and -3 are rated for the same supply range, but they are given their respective power specs at different supply voltages. If you look at the power curves, they make no distincion between the -1, -3, and -4 variant, leading me to believe that the power stages are all very similar, if not identical.So far, I think floobydust’s explanation makes the most sense. What might (and likely does) change between the different suffixes is the constant current biasing network for the class AB stage. These may be tailored to/optimized for different supply voltages.If so, you’d think they’d characterize the quiescent current draw over a variety of conditions and for the different variants.But alas, it is an LM386 after all.By the way, I’m not currently working on this project. Its been complete for several years now. Just wanted to document it a little. One day maybe I’ll even replace the LM386 circuit with something a little better.

author: TimNJ
author_rank: Super Contributor
timestamp: September 03, 2018, 03:49:32 am
content: Quote from: HB9EVI on September 02, 2018, 05:53:57 pmTDA7052 is obsolete too!TI makes a lot of <5W amplifier ICs, mainly aimed at laptops, and portable electronics. But they are definitely improvements over the LM386. Lots of Class D stuff and a couple of Class AB stuff still in the mix.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 03, 2018, 09:20:19 am
content: And? They are for sale and will be for quite a while more; the same goes for the TBA820.If you don't have a series production, it really doesn't matter

author: floobydust
author_rank: Super Contributor
timestamp: September 03, 2018, 06:45:39 pm
content: In 1972 theLM380came out, the mother of a few NS chipamps. LM386, LM388 etc.The LM386 goes back to at least 1973.That's 45 years now.Surely it has some Robert Dobkin in it, seeing his lateral PNP (complementary Darlington) output stage with the notorious "bottom side fuzzies" at 5-10MHz."... Because of the lack of a high current PNP transistor in present monolithic technology, the PNP power transistor must be simulated by using a lateral PNP transistor and two NPN power transistors in a composite connection. The difficulty in using such a composite PNP transistor stage is that the phase shift through the lateral PNP transistor permits only a small overall loop transmission. This limits the performance of the amplifier. The time delay through the lateral PNP transistor also causes the local loop of the composite connection to have a very poor gain and phase margin. "Motorola had the 1970US patent 3693107for an all NPN (quasi-complementary) output stage which ended up being the best, for chipamps. It's strange inventor Ernst L. Long later wrote app notes for National.I think this IC ended up kind of crappy due the sea of IC patents on lateral transistors and amplifier architecture.

author: TimNJ
author_rank: Super Contributor
timestamp: September 03, 2018, 08:34:41 pm
content: Quote from: HB9EVI on September 03, 2018, 09:20:19 amSure you can use TDA7052, if you want. I’m just saying, if you’re going to go through the effort of designing somehing new, that perhaps someone else might want to make in the future, you might as well use a part that will available.

author: TimNJ
author_rank: Super Contributor
timestamp: September 04, 2018, 02:31:40 pm
content: Quote from: floobydust on September 03, 2018, 06:45:39 pmVery interesting thanks for the history lesson!