Lm386 Audio Amplifier Circuit- Creating Different Amplification Functions

If you are a music enthusiast, you fancy loud sounds at times. To obtain high sound quality audio and bass boost, you will need a well-built device. Nonetheless, do you know that you can modify audio quality with a minimum budget? All you require is a good output device and an LM386 Audio Amplifier Circuit. This operational amplifier will boost the sound quality to the desirable levels depending on the supply voltage. You will find it in all common audio devices, such as an MP3 player.

Do you know how it functions? If not, relax as we will explain it all.

1. What is LM386 Audio Amplifier Circuit?

An Illustration of Speakers 

An LM386 Audio Amplifier Circuit is a simple circuit like that of any other operational amplifier. It takes audio input from the audio source and amplifies it. Typically, an  LM386 Audio Amplifier Circuit features a default gain of 20. Thus, using it without external components will boost the audio input by twenty-fold.

You can, however, increase this voltage gain by adding external components. The maximum possible amplification that you can obtain is 200 times. Therefore, audio amplifier circuits are the ultimate audio frequency boosters. 

The LM386 Audio Amplifier is compatible with low power supply sources like a 9V battery. For instance, an MP3 player, radio, and even portable audio player use this circuit. Hence, you will find the operational amplifiers in all low voltage consumer applications.

2. Lm386 Audio Amplifier circuit Features

A Sound Amplifier System

An Lm386 audio amplifier is among the most simplistic operational amplifiers. Some of its key features include:

• You can operate it on a single power supply. The amplification circuit can efficiently run on a 6V battery source. 
• It requires minimal external parts to function. 
• It offers a wide range of voltage gain that ranges from a default of 20 to a maximum of 200. You can thus increase sound to a maximum of 26 decibels when you use it without external components. With the components, the audio amplification can rise to 46 decibels. 
• It guarantees low Total Harmonic Distortion (THD) of approximately 0.2% at a frequency range of 500 Hz to 1000Hz.
• It features a low quiescent current drain at approximately 4mA
• You can operate it on a wide voltage range of either between 4V to 12V or 5V to 18V
• You can reduce its voltage gain by using a resistor in series 
• Its frequency bandwidth is 300kHz.  
• It does not require a heat sink as it produces low heat. 
• It comprises eight functional pins. 

3. Lm386 Audio Amplifier Circuit Specifications

Speakers  

There are many kinds of this amplification circuit. Among the common ones include the LM386N-1, LM386N-3, and LM386N-4. Also, each one of them features a unique power rating.

The power rating is the determinant of the maximum sound of the output. For instance, the LM386N-1 amplifier has lesser Watts.  Thus, it will give significantly lower sound quality. The LM386N-4, on the other hand, has a higher power. Consequently, it will provide you with higher sound quality than the former.

Other critical specifications include:

• • Supply Voltage (Vcc)

  It would help if you had a minimum supply voltage of 4V. The upper range of the supply voltage is 12V.

  • Speaker impedance

  The original designation of the Lm386 audio amplifier is a 4Ω speaker load. Nonetheless, you can still use it for 8Ω and 32Ω loads and obtain audible sound.

  • Distortion

  In the best conditions, you will have a 0.2% total harmonic distortion (THD). For this, you need a 6V power supply and an 8-ohm, One-watt speaker.

  • Output power

  You can obtain approximately ~700mW of output power with this speaker. It is close to 0.7W of clean output power.

  The marketing hype with speakers may have you thinking that maybe 0.7W is not sufficient output power. However, it is enough for your laptop speakers and your mobile phone use. This power will provide more than adequate sound, especially when you use headphones.

4. Three Based LM386 Audio Amplifier Circuit

An eight-pin operational amplifier

You can make different types of LM386 audio amplifier circuits depending on the available components. First, you must understand the primary functions of every pin on the chip. There are eight pins on an LM386 chip. 

The function of pins 1 and 8 is to adjust the gain level.

On the other hand, the 2nd and 3rd pins function as the negative and positive input of the system. Ensure you connect the negative input to the ground. Also, join the positive input to the audio signal source. 

Pins 4, 5,6, and 7 are the Ground (GND), op-amp output, Voltage Supply pin, and bypass, respectively. 

After you identify the pins, you can create any amplifier circuit. Some of the common audio amplifier circuits include the following: 

• A Minimal LM386 Audio Amplifier Circuit

Several LM386 Audio Amplifiers 

For this circuit, you require these components:

• A 9V supply voltage
• 8-Ohm Speaker,
• 10Ω resistor,
• 1000μF supply capacitor
• 0.1 μF capacitor
• Audio player
• Audio input wires
• Volume control

A cheap breadboard

LM386 audio amplifier

During connection, you can have the input ground in the same wire as the output ground. However, such a connection will yield a noisy output ground. Consequently, this will damage the input signal. The input signal is sensitive to noise. Therefore, such a connection will amplify the noise. It will, as a result, lead to distortion of the sound quality.  

You can avoid this challenge by assigning the input ground its unique path. However, you can connect other terminals. Nonetheless, ensure they are not in the same channel as the input ground. This second connection will give an improved sound quality than in the erstwhile assembly. 

• A Great Sounding LM386 Audio Amplifier Circuit

A sound wave

You can improve on the effectiveness of the former circuit with this version. It will give you enhanced adjustable gain control.

During connection, you need to make several modifications to improve the sound quality. They include:

• Consider placing a low capacitance capacitor in between the ground and the third pin terminal. Resultantly, the capacitor will act as a filter to block the radio interference in the connecting cables.
• Also, place a relatively high capacitance capacitor and low capacitance capacitor between the second and third pin terminals. These capacitors will act as frequency noise filters to improve the sound quality.
• Additionally, put a low capacitance capacitor between the 4th and 6th pin of the LM386 audio amplifier. It will further prevent the undesired coupling of the power supply.
• Lastly, align the resistor with a capacitor between the ground and the 7th pin. It will allow you to prevent the undesired coupling of the audio input signal. It is essential in improving the sound signal.

Note: When connecting the LM386 Based Audio Amplifier Circuit, you must keep all the components close to the Op-amp. Also, ensure that you maintain short wire distances. These precautions will enable you to obtain an improved audio quality.

• The LM386 Audio Amplifier with Bass Boost Circuit

 A Wall of Speakers

With an LM386 based amplifier, you can ensure that you have a bass boost to the output. A bass boost will operate as a low pass filter to eliminate all the noise the other filters cannot exclude. You can easily create the bass boost circuit.  For this, you require a low capacitance capacitor and a potentiometer. Since the bass boost is an external component, you have to connect it to pin 1 or 8.  Connect these components in series between the 1st and op-amp’s voltage output pin. For this system, you need the following components:

• 100 μF capacitor
• 0.1 μF ceramic capacitor
• 0.033 μF ceramic capacitor
• Two 10 μF capacitor
• An LM386 audio amplifier chips
• A speaker
• A 9V battery
• A cheap breadboard
• Audio input wires

5. How to create an LM386 Audio Amplifier Circuit?

 A young woman enjoying music

• Creating a simple LM386 Audio Amplifier Circuit is relatively straightforward.
• Steps to a simple circuit:
• After you identify the pins, you can now connect the circuit using the following directions:
• Attach an audio input signal to the positive input pin of the Op-amp. You must ensure that you connect the audio path to the GND. Also, ensure that you attach a high-value resistor, preferably 10KΩ between the input signal and GND. This resistor will operate as a pull-down resistor to ground the input when there is no source. If you do not connect this resistor, you will experience a loud hum before connecting the audio source.
• If you want the default gain of 20, don’t connect any external component. Nonetheless, if you wish for a higher gain, connect components on the 1st or 8th pin.
• Next, place a 100uf capacitor between the bypass pin and the ground. It will prevent the amplification of the power supply noise.
• Also, ensure that you connect the negative input terminal and the GND pin to the ground.
• Connect the power source through the voltage supply pin. You must ensure that you place a 100uf decoupling capacitor parallel to the voltage supply pin. It will help in filtering low-frequency noise.
• Lastly, connect the op-amp output to a speaker. It would help if you placed a 0.1μf capacitor and a 1000μf capacitor parallel to the GND. The 0.1μf capacitor will filter high-frequency noise while the 1000μf capacitor will filter and smoothen the sound quality.

 Conclusion

As you have seen, an LM386 Audio Amplifier is an op-amp that improves sound quality. The Will operate on a low voltage supply and does not necessarily require external components to function. It features a default gain of 20, which you can increase up to 200. It makes it versatile for all audio amplification needs.

We have further profound insights into other kinds of amplifiers. Reach out to us, and we will explain everything that you need to know promptly.