Instructables
Picture of Know Your IC: LM386
Welcome to the next installment of "Know Your Integrated Circuit"!

Know Your IC seeks to demystify common Integrated Circuits and allows people to understand them to a point where they can use them in their own projects.

This episode will feature the LM386 a popular op amp chip. We will go over the chip functions and a bit of history.

And we will teach you how to build a simple amplifier with the chip!




 
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Step 1: Introducing Op Amps

Picture of Introducing Op Amps
Op-amps are a little hard to explain, but essentially they take something small and make it big!

Op-amps are perfect when you need to take a signal and have it go much higher than the original, for example doing audio amplification.  Wikipedia has a great history of the op-amp and it's development. 

LM386 is made specificly for low voltage applications. Different op-amps will have different requirements, always check out the data sheet! The LM386 can take 4V-12V or 5V-18V depending on the wiring and pump that up 20 to 200 times.

You can use this chip to build any of the following:
AM-FM radio amplifiers
Portable tape player amplifiers
Intercoms and
Small Servo Drivers


Step 2: Pin-Outs

Picture of Pin-Outs
The pin-out of the LM386 is as follows:

Pin 1: Gain
Pin 2: Input -
Pin 3: Input +
Pin 4: Ground
Pin 5: Vout (Output)
Pin 6: Vs (Power)
Pin 7: Bypass
Pin 8: Gain

The input obviously goes to pins 3&2. The most interesting part about this chip i feel is the gain function. If you put a capacitor between pins 1 and 8, you can control the amount of gain the amp has. The bypass allows you to access the input un-amplified, if you so desire.

Step 3: Project: Audio Amp

Picture of Project: Audio Amp
Our project we will be doing to demonstrate the LM386 is a simple audio amp. A similar design is used in "cracker box" amps.

This version is completed using minimal parts, you will need:
1 LM386
1 10 Ohm Resistor
1 220uf Electrolytic Capicitor
1. .047uf Film Capicitor
1 9v battery
1 10k Ohm Potentiometer
1 8ohm Speaker
1 1/8" mono audio jack
some solid hook up wire
1 breadboard
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Bozho6 days ago

Hi, I have a question regarding the LM386. I saw some schematics online that feature this amplifier, and in most of them pin 2 (- input) was grounded, and input signal with a 10k potentiometer is hooked up to pin 3 (+ input). I was wondering, why is pin 2 always grounded, and can we use this IC in a negative feedback configuration as we do with a standard operational amplifier, such as LM741? Thanks in advance.

Raphango17 days ago

Excellent! =D

Raphango17 days ago

Excellent! =D

Gisty227 months ago

can i put female audio jack instead of the speaker so i can connect it to my transmitter

natere21 Gisty222 months ago

Yes. This is exactly what I did. I have a 1/4" TS (tip, Sleeve) audio jack instead of the TRS 1/8" mini plug shown in the tutorial.

natere21 made it!2 months ago

Thanks for the tutorial! nice little mono preamp. all you need is 2 of these, an regulated power supply (filtered!) and some power gain stages for an nice DIY stereo amp! :)

lm386amp 002.JPG
Dr_momo3 months ago

Hi All,

I'm buying the parts to get started with this instructable, one thing is confusing me, what voltage is the .047uf film capacitor supposed to be? There are a bazillion options and I am totally new to electronics...help!

Many thanks.

joesinstructables made it!6 months ago

Worked perfectly, thanks for posting.

image.jpg
LM386 circuit.MOV(516x290) 18 KB
jdoeson1 year ago
What's the point of the .047uF capacitor and the resistor coming off pin 5? They don't seem to be necessary in my setup (part of the GND line?)

I'm using the 250uF film capacitor, but I tried using a few electrolytic capacitors that also worked fine (though had small volume differences): 100uF, 470uF and 1000uF.

I'm actually using this for a "HDD speaker". It sounds ok, and I can make the HDD actuator move pretty well with this, though I think I need to boost the voltage to make that sucker really dance.
foggy34 jdoeson9 months ago

Hey, im wondering the same question as you about the 250uf cap. i have a set of plans that says to use a 10uf cap. but i cant get the thing to work...grr. when you tried the 1k and the 100 which was louder? thank

gauzz1 year ago
What is the difference if i use it with different voltages, I plan to make one that works at 12 volts so if I use a 9v battery or a 5 volts regulator will it sound lower?
LGT3001 year ago
Can i use a 5k potentiometer
jdoeson1 year ago
Sorry I meant the 250uF electrolytic cap not film. The .047uF cap is film, and unused in my project.
jdoeson1 year ago
By the way - thanks for this instructable. A learning experience for us novices.
tealk1 year ago
hey! another question. can i use 50K potentiometer?
tealk1 year ago
hi, do i need to use potentimeter? can i use 10k ohm variable resistor like this http://www.mikroprinc.com/proizvodi/pasivne-elektronske-komponente/otpornici/promenljivi-otpornici/trimer-potenciometri/jednoobrtni-trimer-potenciometri/pt10l-10k/index.php?
voltronvw2 years ago
Hi, I got the amplification alright but the potentiometer won't adjust volume. It's
a 10k audio taper potentiometer 250vdc .25w ..I had continuity between
1st and 2nd connectors on the potentiomenter so I believe its functional...
any ideas?
make sure you add the wires to the top part of the potentiometer the bottom is for the battery
AlexMayu2 years ago
I was wondering if I need any of the resistors and capacitors for pin 5 if for instance I'm just analyzing the output signal from pin 5 using an analog pin on a Arduino.
art.z3 years ago
Hi, I have a question.

Is a 220uF 35V capacitor enough for the output? Or it will have to stand higher voltages?
I noticed that the capacitor I have is smaller than the one you're using and I don't have a voltage meter to make sure.

Also, do I ground everything on the negative pole of the battery? Even pin 4?

Thank you!
Ririshi art.z2 years ago
Pin 4 IS the ground of the chip. Just think of putting a little lamp in a circuit to a battery, you would do the same thing. All other things with the gnd sign go to the - of the battery, too. I think your cap is enough, as I use a 10V and it didn't burn (lol).
jimmy5582 years ago
nice design...
but can clear the whole circuit of breadboard coz we not geting which pin of ic is connected with which components, plz make an other clear picture and also write info in description plz.
kenkaniff3 years ago
I'm still new to circuits, and there's one thing I don't understand about your pictures...

Where exactly does the 9V battery connect to?
it plugs into pin 6 and 4 i think.
I'll have to test that before I do any soldering.

Thanks!
i believe 6 is the + and all the other ones with three lines are - and the other V in is also + for the potentiometer (variable resistor).
Awesome thanks.
Thanks! I've been looking for a simple explanation to op-amps for a while. This is a great instructable.
gmuñoz12 years ago
I liked the model. But where the battery is connected?
Misac-kun3 years ago
and if you put an potentiometer on pins 1 and 8? will it be able to control the volume?
art.z Misac-kun3 years ago
You will be able to control the gain!

I'm pretty sure It's the same thing!
But I saw another instructable that put 2 potentiometer, 1 between pins 1 and 8 and 1 before the speaker! (Weird)
David97 art.z3 years ago
I saw a datasheet explaining the gain and how to control it.
David97 David973 years ago
It says in application hints. 'If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200.'
So, i've been working with these chips, trying to build a noisy Cricket. but i think i killed both the ones i have. is there any way to tell if i really killed it?
Rolcrz3 years ago
Hello! I read through your instructable and found it very useful and easy to follow. However, when building the actual circuit and powering it on, I encounter a peculiar problem: I seem to be catching radio stations! Even if I connect the jack to my mp3 player, all I hear is the same darned radio station! Any idea what could be causing it?
hi frenzy......i need help on LM 747!
Thank a lot!
Thank You!  This is a great series.
-TTR
REA3 years ago
of course this 'ible comes to my attention after i break the second pin. -_-
WerdnaN3 years ago
I believe that pins 2 and 3 are inputs, not outputs.
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