LM386 Audio Amplifier IC Structure, Working Principle, Manufacturer, Function and Applications
23 February 2024
Ⅱ. Internal structure and working principle of LM386
Ⅲ. Pins and functions of LM386
Ⅴ. What is the function of LM386?
Ⅶ. What are the applications of LM386?
LM386 is an audio power amplifier produced by National Semiconductor. It is mainly used in various low-power, portable audio equipment, such as electronic clocks, radios, and small speakers. This article mainly introduces it from the aspects of structure, working principle, manufacturer, function and applications.
The LM386 is a low-voltage power amplifier suitable for DC power supply voltages between 4V and 12V. It provides high-gain audio amplifier functionality in an 8-pin DIP or SOIC package with the help of a single coupling capacitor and two regulator tubes. The chip features low noise, low distortion and low power consumption, making it ideal for battery-powered electronic equipment.
Alternatives and equivalents:
• BA546
• KA386
LM386 consists of an input stage, intermediate stage and output stage, as well as feedback and bias circuits. Among them, the input level is divided by the input resistor and enters the differential amplifier for signal amplification. Because it contains a large number of stages, it can ensure that the output current and power are very stable.
The working principle of LM386 is based on the amplifier of internal transistors. Its input signal is amplified and sent to the amplifier circuit. At the same time, feedback gain control is performed through the feedback circuit to achieve the required amplification factor. Compared with other audio amplifiers, the LM386 is special in that its input impedance is very high, while it can also operate normally at low voltages and consume very little current.
The LM386 audio amplifier consists of 8 pins, and its pin configuration is shown in the figure below:
Pin 1 (Gain): This is the gain pin, which adjusts the amplifier gain through external component capacitance.
Pin 2 (Input-): This is the non-inverting pin used to provide the audio signal.
Pin 3 (Input+): This is the inverting terminal, usually connected to ground.
Pin 4 (GND): This is the ground pin, connected to the ground of the system.
Pin 5 (VOUT): This is the output pin, used to provide amplified output audio and connected to the speaker.
Pin 6 (Vs): This pin is connected to the power supply.
Pin 7 (Bypass): It is used to connect the decoupling capacitor.
Pin 8 (Gain): It is the gain setting pin.
The LM386 is manufactured by National Semiconductor. The company, headquartered in Santa Clara, California, is a leading developer of analog power management technology and produces a wide range of power management products, including PowerWise products designed to improve system energy efficiency, easy-to-use integrated circuits, and SolarMagic products that increase the amount of power generated by solar energy systems. The company has now been acquired by Texas Instruments (TI) and on September 23, 2011, the official merger was completed.
Its main functions can be summarized as follows:
1. Protection function: LM386 has some internal protection functions, such as overheating protection, overcurrent protection, etc. When abnormal conditions occur during circuit operation, these protection mechanisms will be automatically triggered to protect the safety of circuits and equipment.
2. Power management: The LM386 chip integrates a power management circuit, which can regulate and stabilize the input power to provide stable operating voltage and current. This can ensure the normal operation of the power amplifier circuit and effectively prevent the impact of power supply noise on the audio signal.
3. Signal amplification: LM386 can amplify the input audio signal, making the sound clearer and louder. By adjusting the gain control resistor in the circuit, it can achieve different amplification factors to meet different audio needs.
4. Output drive: The output end of the LM386 power amplifier circuit can directly drive devices such as speakers or headphones, so that the audio signal can be output at appropriate power, thereby producing clear, high-quality sound effects. By adjusting the output resistance in the circuit, it can adapt to different load requirements to obtain the best sound quality.
The LM386 only requires a few capacitors and resistors to start working. A commonly used LM386 circuit is shown below:
This IC uses pin 6 for power (usually 5 or 9V), while ground pin 4 is connected to ground. The inverting pin (pin 2) is usually connected to ground, while the non-inverting pin (pin 3) provides the audio signal. These audio signals can originate from a microphone or even be plugged in via a 3.5mm jack. A 10k ohm resistor is placed in series with the audio signal and is used as the volume control. We can choose to ignore this potentiometer if we wish to operate at full volume. Pin 1 and Pin 8 are used to set the gain of the amplifier. If there is no connection between these two pins, the default gain is 26 dB; but if a 10 microfarad capacitor is connected across them, we can obtain the maximum gain of the IC, which is 46 dB. Pin 7 is used to connect the filter capacitor (0.1 microfarad) of the amplifier IC to eliminate unnecessary oscillations. The amplified audio signal can be connected to an 8 ohm speaker through pin 5, through a filter capacitor. Additionally, an RC network consisting of a 0.05 microfarad capacitor and a 10k ohm resistor is optional.
LM386 can be used in the following fields:
• Sound detector: LM386 can be used to design sound detectors. By connecting appropriate sensors, we can utilize LM386 to detect sound in the environment and amplify its output to trigger other circuits or devices.
• Portable devices: LM386 is especially suitable for use in some portable electronic devices that have more stringent power requirements, such as small radios and portable speakers. In these devices, the LM386 is able to provide clear and stable audio output while maintaining low power consumption, thus extending the overall usage time of the device.
• Audio amplification circuits: The LM386 can be used to amplify audio signals, such as those from audio sources such as microphones, MP3 players, etc., to drive speakers or headphones.
• Video games or toys: The LM386 can be used to design sound effect modules for video games or toys. For example, in a toy car, the LM386 can receive weak signals from a microcontroller or other audio source and amplify them to drive speakers to produce realistic engine sounds. And in electronic games, it can receive commands from the game controller and amplify the corresponding sound effect signals according to different game situations and actions.
• Electronic doorbell: LM386 can be used to design doorbell circuits. By connecting a trigger to LM386, when someone presses a button, LM386 will amplify the sound signal from the trigger to produce a loud doorbell.
• Small speaker or speaker amplifier: The LM386 can be used to design simple small speaker or speaker amplifier. When designing, we can precisely control the gain and volume by adjusting the parameters of the external circuit. For example, by changing the values of the resistors and capacitors connected to the LM386, we can adjust the gain of the amplifier, i.e. the amplification of the audio signal. At the same time, by adjusting the potentiometer or other volume control components, we can also easily control the output volume to meet different occasions and listening needs.
Frequently Asked Questions
1. What is LM386 used for?
The LM386 is an integrated circuit containing a low-voltage audio power amplifier. It is suitable for battery-powered devices such as radios, guitar amplifiers, and hobby electronics projects.
2. What are the disadvantages of LM386?
There are various kinds of amplifiers can be built with the help of IC LM386, but the main drawback of this circuit is interference as well as noise. The proposed system can be designed with less noise.
3. What is the difference between LM386 and lm741?
The LM386 has inputs that work at its negative supply voltage that is usually 0V (ground). The 741 has a max output current of about 20mA so it can drive a load of 2000 ohms. The LM386 has a max output current of about 810mA so it can drive an 8 ohm speaker. The 741 needs negative feedback resistors added.
