0
\$\begingroup\$

I am not an electrical engineer, but I am curious enough and my mind tells me to make a radio circuit.

Now I am into it, so to make one, I need some components, but before that so that I can be a little more into basics of the working of the device, the only device I can't find an explanation for is the LM386 IC.

It is an audio amplifier but its pin-out is not that clear. It shows a simple triangle but no information.

What is it? A logic gate, another IC?

Please explain to me how the LM386 works.

\$\endgroup\$
11
  • \$\begingroup\$ Copy and paste the picture that has the triangle from the data sheet \$\endgroup\$
    – Andy aka
    Aug 10 '20 at 17:18
  • \$\begingroup\$ Just a general remark: The LM386 is a terrible amplifier. Really, no matter what you do, there's better ones, that aren't much harder to get. The LM386 was invented 1969. That's 51 years in the past. It sounds terrible, and was replaced by more reliable, more efficient, easier to use correctly, and most importantly: better sounding ICs since then. \$\endgroup\$ Aug 10 '20 at 17:55
  • \$\begingroup\$ @MarcusMüller There are better, mostly in the pre-amplification side -- which really should be designed for the input source and not just developed generically if you want the S/N as good as possible. There are better in the sense of being bridged (two amps inside) and therefore easier to generate more power from a given rail voltage. But it and the LM380 have global NFB that can be adjusted and I'm curious what class-AB amplifier ICs you like, in particular. (I don't ever use the LM386. I'm just curious what class-AB IC you like.) \$\endgroup\$
    – jonk
    Aug 10 '20 at 18:24
  • \$\begingroup\$ SHikha, see this LM380 discussion for some thoughts. It's not the LM386, but you can compare the schematic with the LM380's by referencing the schematic on the LM380 datasheet. You'll see a lot of similarity. \$\endgroup\$
    – jonk
    Aug 10 '20 at 18:27
  • 1
    \$\begingroup\$ @MarcusMüller I definitely use the TDA family. My first was the 1 W TDA8551. The class-D are way out of the capability for many hobbyists to correctly design for, though they can just use them. That last project you describe sounds like over-kill to me. But then I'm old enough now that hearing is declining and really nice acoustics into my brain is no longer much of a possibility. \$\endgroup\$
    – jonk
    Aug 10 '20 at 18:49
3
\$\begingroup\$

The LM386 is an IC. The triangle is just a symbol use on a schematic diagram to represent the IC.

If you consult the manufacturer's datasheet for the LM386, you should find a full description and schematic of the internal circuit, and also a description of the physical package of the part, with the dimensions and pin locations.

\$\endgroup\$
0
\$\begingroup\$

The LM386 is an audio power amplifier. "Power" in this case usually is less than 1 watt. In a sense it is a specialized version of an operational amplifier, so it usually is shown on a schematic with an opamp-like symbol.

Here is the datasheet from the company that invented it: https://www.ti.com/lit/ds/symlink/lm386.pdf

Only one of the schematics in the datasheet shows a decoupling capacitor across the power pins, but it is critically important that it be there for any/all circuits. The capacitor(s) should be as close as possible to pins 4 and 6, with the shortest possible leads. I recommend a 0.1 uF ceramic and 10 uF electrolytic in parallel. All audio power amp chips are very sensitive about this.

\$\endgroup\$
4
  • \$\begingroup\$ I don't think TI invented LM386 though. \$\endgroup\$
    – Justme
    Aug 10 '20 at 17:34
  • \$\begingroup\$ @Justme no, that was Motorola. 1969. \$\endgroup\$ Aug 10 '20 at 17:53
  • \$\begingroup\$ @MarcusMüller - Are you sure it wasn't National Semiconductor. The LM prefix is used for all their devices (I think it is an acronym for Linear Monolithic). Motorola numbers all began with MC. TI now owns National Semiconductor. \$\endgroup\$ Aug 10 '20 at 23:13
  • \$\begingroup\$ National invented the LM386 as a stripped-down version of the LM380. TI bought National and all of their designs and documents. The old Motorola part has the same number, but I don't think it is the same part. The LM385 we are talking about is not something for an automotive fuel injection system re-purposed for consumer audio. \$\endgroup\$
    – AnalogKid
    Aug 10 '20 at 23:44
0
\$\begingroup\$

Here is a pinout diagram of the lm386. And I believe this is its most general format.

lm386 pinout

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.