Project your circuit of the audio amplifier with the ic lm386 lm386n lm386n-1. General description of the ic lm386. The LM386 is a power amplifier designed for use in low voltage consumer applications. Operational amplifiers have a basic task. They take an input potential (voltage) and produce an output potential that’s tens, hundreds, or thousands of times the magnitude of the input potential. In an amplifier circuit, the LM386 takes an audio input signal and increases its potential anywhere from 20 to 200 times.
Make a Great Sounding LM386 Audio Amplifier with Bass BoostIn this tutorial, I'll first show you how to make a basic audio amplifier with an LM386 IC to demonstrate the minimum parts needed to build a functional amplifier. Then I'll build a much better sounding amplifier by adding multiple de-coupling capacitors to the power supply and the input and output signal lines. Lastly, I will add a bass boost control to the circuit.LM386: full tutorial can be found here: out the Circuit Basics blog for articles and tutorials on the Raspberry Pi, Arduino and other DIY electronic projects! Twitter: Instagram: http://www.instagram.com/circuitbasics.
In this tutorial, I’ll show you how to build a great sounding audio amplifier with the LM386 Low Voltage Audio Power Amplifier. I built about a dozen different audio amplifier circuits with the LM386 but most of them had way too much noise, popping, and other interference. Finally I found one that sounds great, so I’m going to show you how to build it.It’s not a “minimal components” audio amplifier. I added a bunch of extra capacitors to reduce the noise, and I added a bass boost control as well to make it sound even better. But before we start building, it might be helpful to get a little background information firstLM386 BASICSThe LM386 is quite a versatile chip. Only a couple resistors and capacitors are needed to make a working audio amplifier. The chip has options for gain control and bass boost, and it can also be turned into an oscillator capable of outputting sine waves or square waves.
There are three varieties of the LM386, each with different output power ratings: LM386N-1: 0.325 WattsLM386N-3: 0.700 WattsLM386N-4: 1.00 WattsThe actual output power you get will depend on your supply voltage and speaker impedance. The datasheet has graphs that will tell you. I used a 9V battery for the power supply and it works great, but you can go down to 4V or up to 12V. The LM386 is a type of operational amplifier (Op-Amp). Operational amplifiers have a basic task.
They take an input potential (voltage) and produce an output potential that’s tens, hundreds, or thousands of times the magnitude of the input potential. In an amplifier circuit, the LM386 takes an audio input signal and increases its potential anywhere from 20 to 200 times.
That amplification is what’s known as the voltage gain.GAIN VS VOLUME After you build this amp and play with the volume and gain controls, you’ll notice that both appear to raise or lower the intensity of sound coming out of the speaker. So what’s the difference then? Gain is the amplification of the input potential and is a characteristic of the amplifier. Volume lets you adjust the sound level within the range of amplification set by the gain. Gain sets the range of possible volume levels. For example, if your gain is set to 20, the range of volume is 0 to 20. If your gain is set to 200, the range of volume is 0 to 200.
Gain control can be achieved by connecting a 10 μF capacitor between pins 1 and 8. Without a capacitor between pins 1 and 8, the gain will be set to 20. With the 10 μF capacitor, the gain will be set to 200. The gain can be changed to any value between 20 and 200 by placing a resistor (or potentiometer) in series with the capacitor.
A MINIMAL LM386 AUDIO AMPLIFIER Now that we have a little background information on the LM386, let’s start by building a bare bones LM386 amplifier with the minimum amount of components needed to make it work. That way you can compare it to the better sounding one we’ll build later on.On the top is the schematic and the way you have to wire it if using a bread board.In the wiring diagram above, the audio input ground flows through the same path as the audio output ground.
The output ground is “noisy” and will cause distortion in the input signal if it’s wired this way. The audio input ground is sensitive to any interference and any noise picked up will get amplified through the amplifier. Make it a goal to keep the input ground separate from other ground paths as much as possible. For example, you can connect the grounds for the power supply, input, and output directly to the ground pin (pin 4) of the LM386 like this. A GREAT SOUNDING LM386 AUDIO AMPLIFIERNow that you’ve seen the bare minimum of what it takes to make an audio amplifier with the LM386, lets build a higher fidelity version with an adjustable gain control.
Note: Most of the component values in this circuit aren’t critical. If you don’t have a particular value, try substituting something close and it will probably work.Several things in this circuit make it sound better: A 470 pF capacitor between the positive input signal and ground, which filters radio interference picked up by the audio input wires.100 μF and 0.1 μF capacitors between the positive and negative power rails to decouple the power supply. The 100 μF capacitor will filter low frequency noise while the 0.1 μF capacitor will filter high frequency noise.A 0.1 μF capacitor between pins 4 and 6, for additional decoupling of the power supply to the chip.A 10K Ohm resistor and a 10 μF capacitor in series between pin 7 and ground to decouple the audio input signal.One thing to keep in mind when you’re wiring any audio amplifier is that the cleanest sound will result from keeping all wire connections and components as close to the chip as possible. Keeping the wires as short as possible will also help.
A cool feature of the LM386 is the option to add an adjustable bass boost to the amplifier. You’ll probably find that this is the best sounding circuit. The bass boost is basically just a low pass filter, and it removes most of the noise not taken out by the decoupling capacitors. All you need for the bass boost circuit is a 0.033 μF capacitor and a 10K Ohm potentiometer in series between pins 1 and 5:An easy way to connect the audio input in these circuits is by cutting the 3.5 mm audio jack from an old set of headphones and wiring it to breadboard pins.Thanks for reading! Hope you had fun experimenting with these amps as much as I did. If you’re ready to build some even better sounding and more powerful amps, we have tutorials on a few others: The LM3886 is by far the best sounding amplifier, but it’s a fairly involved project.
If you’re just starting to build audio amplifiers, I’d recommend working your way up to it by starting with the TDA2003, then moving up to the TDA2050.Hoping for positive responses for my hard efforts!:).
Audio is one of the most entertaining, time-consuming and (eventually) wallet-draining ways of learning about and falling in love with electronics. Reproducing, recording and amplifying audio gets you up close and personal with the electrons rocketing through your circuits.Which brings us to what is in my mind the best kickoff point in learning about audio electronics - amplification. If you have access to an old speaker and an audio source (such as your phone or MP3 player) you can easily start building low cost circuits that have immediate results - music blasting into the airwaves. Chip AmpsIt used to be that audio amplification depended on large numbers of discrete components or power-hungry vacuum tubes to get decent sound from a source to a speaker. Like everywhere else, integrated circuits have made the barrier to entry much lower, letting us use any number of op-amps designed specifically for audio. These ICs are collectively called audio amplifier ICs, amplifier chips or chip amps.
Typically they require few external components, can be prototyped with simple circuit designs and require less current than their discrete and tube counterparts.Which brings us to the venerable LM386 by Texas Instruments. This bad boy has been with us since 1983, and can still be found in low power, battery driven applications all around the world. And being. easy to power (using a single supply). low heat (no heatsink required). efficient.
available in the prototyping-friendly DIP package.means it's much loved by the DIY audio community and a terrific place to start experimenting with chip amps. Also, you can pick one up for around $0.50 USD:) Here we'll learn about the chip and build a simple circuit to put it to work.
Let's take a look. A good place to start is the (PDF) where you can get all the technical information you need. But I'll go over the basics here.The LM386 is an operational amplifier than has been specifically designed for use in audio applications.
Which means its performance is based on the assumption that it will be driving speakers. At least at some point. However it can, like most other basic audio amplifier chips, be used as a regular op-amp as well.It has a default gain of 20x - meaning it will multiply the voltage it receives on the input by 20 times, passing this through to the output. The gain value can be adjusted if needed. The pins1, 8 - Gain Pins 1 and 8 are used to adjust the gain level from the default 20x using specific values of connected capacitors.2 - Negative Input 3 - Positive Input These are the standard op-amp inputs. Typically in a simple LM386 circuit, the negative input will be tied to ground while the positive input will receive the audio signal from the source.4 - GND5 - Vout Pin 5 is the op-amp output, in our case the amplified signal which we send on to the speaker.6 - Vs The Voltage Supply pin receives the power required to operate the amplifier.7 - Bypass This pin provides direct access to the signal input, primarily used to remove power supply noise (preventing noise from being amplified).
SpecificationsThe LM386N ('N' signifying the preferred DIP package for our purposes) comes in 4 flavours: LM386N-1, -2, -3 and -4. The '3' and '4' versions have slightly higher output power, with the '4' version more so given its ability to handle more input voltage (at the cost of a higher minimum voltage requirement). Despite the marketing hysteria surrounding power output for speakers and amplifiers, you'd be surprised how loud 1W of output power can be.
While you won't get deep, booming bass, 1W of clean power is more than enough to drive small desktop computer speakers and many mobile audio applications. And in the world of headphones (where the speakers are right next to your eardrums) you're talking a couple dozen milliwatts of power needed to crank up the volume. Here's a useful, myth-busting rule to remember:Doubling output power gains you 3dB of acoustic power.Which means the difference between 50W and 100W is 3dB.The difference between 100W and 200W.
3dB.500W and 1000W? Still only 3dB!So you hit diminishing returns pretty quickly, and get comparatively little increase in perceived volume as you go up the power scale.Side note: The relationship between dB, power and sound pressure is complicated, but essentially you'd need to quadruple the amplifier power to double the sound pressure, which equates into varying levels of loudness depending on the listener. See these great articles to understand more:In fact some of the most celebrated integrated and power amplifiers (such as the legendary ) were capable of delivering 'only' 20W into 8Ω speakers, which by today's standards isn't something the marketing suits would be happy to advertise. But the fact remains that after basic power requirements have been met to drive a specific set of speakers at an ideal volume, factors such as frequency response, total harmonic distortion and transparency are far more important than raw power. Building a basic functional circuit for the LM386 is dead easy. The schematic is a mono amplifier, so if you wanted to amplify a stereo signal you'd need two of these circuits (one for each channel and each speaker).1. We need to supply an audio signal to the +Input of the amplifier (pin 3).
The audio signal also needs its own path to GND. In addition, a high value resistor between the signal input and GND (10KΩ in the schematic) acts as a pull-down resistor that drives the input to ground when a source isn't connected. Without this resistor, you'll get a loud buzz/hum if your music player isn't hooked up.2. Pins 1 and 8 have been left open, as we're using the default gain of 20x.3. A 100uf capacitor is placed between the bypass pin (7) and GND, in order to prevent some power supply noise from being amplified.4. The -Input and GND pins (2, 4) are connected to.
The power source is fed into pin 6, along with a 100uf decoupling capacitor in parallel to GND to filter out low-frequency noise.6. Finally, the output from pin 5 is fed into the speaker, with two more capacitors paralleled to GND: a 0.1uf (100nf) cap to filter out high frequency noise, and a 1000uf supply capacitor for filtering and smoothing. Plug in an old 4 or 8Ω speaker (one you don't mind risking!) and an audio source and slowly turn up the volume. Experiment with different styles of music and see if you can detect any clipping or noise, especially at higher volumes. I found clipping was reached at about 80% volume on my iPhone, but by then it was already louder than comfortable average listening. Try the circuit with and without the various filtering capacitors and see what differences you can hear.
Unplug the audio cable and remove the 10K pulldown resistor to appreciate what that bad boy is doing for you. Turn down the volume and try add a 10uf ceramic capacitor between pin 1 and 8 to increase the gain from 20x to 200x.Experiment, and listen! But when in doubt, keep the volume low and turn it up later.
Stress testUsing a small collection of audio test equipment I've put together, I got the following results while driving an 8Ω dummy load:. With a 1kHz sine wave, a maximum input of 120mV RMS before clipping. Around 2.38V RMS on the output.
Meaning our gain of 20x was pretty much spot on (2380mv / 120mv = 19.83x). 707mW of output power, which significantly exceeded the rated output. But to be fair I was pushing it harder than recommended.THD:Running the circuit through a spectrum analyser for the whole 20Hz to 20kHz audio spectrum got a total of -35dBc average, or 1.7% THD (total harmonic distortion). Not audiophile by any stretch of the imagination, but for a $2 audio circuit on a cheap breadboard, with lightweight cables and unshielded inputs. Not too shabby! We'll leave the 0.0001% distortion for future circuits:). If you like the idea of experimenting with chip amps of higher power, better noise ratings and in more demanding applications, your next steps could be:The LM1875 - an excellent 20W mono audio amplifier that also relies on few external components, although some cooling will be required.The TDA2050 - a 32-35W mono chip that's heading into 'audiophile' territory.
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Don't let that scare you away. You'll need a decent heatsink, some extra external caps and resistors and a little patience. But this baby is capable of some serious performance.And of course.The LM3886, the most widely respected hifi grade DIY-friendly audio chip there is.
Vanishingly low distortion, high power (35-50W) and loads of built in protection mechanisms. Get a fat heatsink!I'll put up new Tales From The Chip articles on these little guys soon, and other audio related Instructables in the near future.Cheers!