• Skip to main content
  • Skip to primary sidebar

Homemade Circuit Projects

Get free circuit help 24/7

Circuits for Beginners | Basic Circuits | LED Driver | Hobby Circuits | Transistor Circuits

New-Projects | Privacy Policy | About us | Contact | Disclaimer | Copyright

Home » Mini Projects » LM4862 Amplifier Circuit – A Better LM386 Alternative

LM4862 Amplifier Circuit – A Better LM386 Alternative

Last Updated on May 5, 2022 by Swagatam 5 Comments

The LM386 based amplifier is still very popular as one of the smallest sized amplifier chips. However, the LM386 is not perfect and has a few drawbacks and limitations.

As shown below, the LM386 works with large electrolytic capacitors, which makes it bulkier and costlier, and causes it to be prone to distortions with age.

Another flaw with LM386 is its input impedance which seems to be very high, allowing the chip to be much vulnerable to oscillations if the inputs are not sufficiently isolated from the output.

Its voltage gain of 20 (or 200 by inserting an additional capacitor) looks quite high for line input level (1 V RMS) and this results in further oscillation issues.

On the other hand, the LM4862 IC is more advanced and slightly more powerful compared to LM386 and it works without any electrolytic capacitor.

Main Features of LM4862

It is designed to deliver 0.675 watt into an 8-ohm speaker with a total harmonic distortion of 1%.

When operated at slightly lower power levels, the distortion is reduced to negligible limits.

Another great feature of the IC LM4862 is its automatic thermal shutdown which protects the chip from damage even if the output is overloaded or short circuited.

This circuit requires just a single 5 V supply for the operations. The input impedance of LM4862 is comparatively low and can be suitably adjusted externally, which ensues that the oscillation issue is kept to minimal.

Internal Layout

The following figure shows the internal structure of the chip LM4862. The output of the IC LM4862 drives the speaker in a differential mode, which involves opposite push pull waveforms driving the speaker across the two output terminals. This differential topology is commonly recognized as BTL (bridge -tied load).

How the LM4862 Works

In the BTL operation the two terminals of the speaker are alternately toggled with a +5V and a 0V depending on the music frequency. This means, the amplifier is able to generate a total of 10 volts swing across the speaker from a 5 volt supply. This is just enough to create a impressive volume of music volume over 4 inch full range speaker.

The chip will work with supply voltage ranging from 2.7 V to 5.5 V. Which means the LM4862 can be powered from two or three 1.5 V AAA cells or a from a computer 5 V USB, or simply from your mobile phone charger.

But remember, the supply must not exceed 5.5 V, and therefore even a 6 V supply can permanently damage the chip.

Total current consumption of the chip can be expected to be around ranges 5 mA in the absence of a music input. and to around 250 mA when it is operated at its maximum volume limit.

Power supply ripple rejection is superb, which is greater than 50 dB when C2 = 1µF.

How to Make an Amplifier using LM4862

A general LM4862 based amplifier circuit can be in the following figure.

It looks very simple without the use of any electrolytic capacitors; which allows it to be cheap and yet have a high-fidelity audio output.

Basically, C2, works like the bias bypass capacitor, which can be a tantalum electrolytic; blocks the audio signal through it.

If possible a 100 µF electrolytic could be added parallel with the C3 to increase stability when the IC is operated with batteries or a poorly regulated power supply. The voltage gain is determined by 2(R2 /R1) that must not be exceed the value of 20.

You can expect the sound quality to be the best when R2 = R1 and the gain is 2. This is exactly what must be followed to drive a speaker when the input is 1 volt from a line input or a headphone jack 3.5 mm.

In case the gain is made higher than 5, it may be necessary to add a bypass capacitor C4 across R2 to prevent oscillation. This can be a 5 pF capacitor, although up to 22 pF capacitor can also be used. But higher values than this may cause problems.

Typically, smaller value resistors can be used like R1 = 4.7K and R2 = 4.7K to 47K, when the input is fed from a low impedance supply. The following image shows us the component values for a few typical typical amplifier set ups.

Note that, the design of the amplifier becomes more efficient in terms of cost and power saving when the bass response is kept at its minimum, although that would also mean the absence of the heavier low frequency notes.

The LM4862 is specified to work with at least a 8 ohm speaker, lower ohms might also work such as 16 ohm, 32 ohm, or 64 ohm speaker, but that may cause the power output to be significantly less.

If you wish to operate the speaker as a single ended output by grounding its one end, you might need to add a series capacitor with the other end of the speaker which is connected with the IC output as shown below:

But single ended operation may drastically reduce the power output from the speaker compared to the differential mode.

Using the Shutdown Pin

Normally, the shutdown pin#1 is connected with the ground line in normal. However, this specific pin can be configured with a button to implement a "mute" function without the need of putting a switch directly on the signal line.

Using the Bias Pin

The bias pin#2 is terminated as the output from an internal voltage divider which is used for maintaining the positive inputs of both the op amps at half the supply voltage so that it becomes possible to power the circuit with a single supply.

The bias pin2 may be further used to bias a couple of more op amps as shown indicated in the following figure.

It may be necessary to bypass the bias pin to ground using any capacitor from 0.1 and 10 µF for improving ripple rejection response and also to suppress the "thump" sound each time the amplifier is switched on.

LM4862 Application Circuits

This little amplifier circuit can be actually used for all applications that require a small audio signal to be amplified to a reasonably high audible level.

AM Radio

A radio receiver circuit is one of these examples, as shown below using a tiny ZN414 AM receiver. Nevertheless, you can use the section of LM4862 stage after the R3 volume control for any similar small audio amplification purpose.

This simple radio will receive all the local AM stations loud and clear over the attached loudspeaker

Square Wave Oscillator

The IC can be also effectively applied as a simple square wave oscillator circuit as shown below:

Bidirectional Motor Control

Although the IC LM4862 is designed to work like an audio amplifier it can well be applied as a full bridge motor driver stage, and the direction of the motor can be changed simply by changing the input logic signals, as demonstrated in the following diagram.

Reference: http://www.ti.com/lit/ds/symlink/lm4862.pdf

You'll also like:

  • 1.  Simple Programmable Timer Circuit
  • 2.  How to Make a Simple 12 Volt LED Lantern Circuit
  • 3.  1000 watt to 2000 watt Power Amplifier Circuit
  • 4.  Make this Simple Buzzer Circuit with Transistor and Piezo
  • 5.  Simple Surround Sound Decoder Circuit
  • 6.  4 Universal Electronic Thermometer Circuits

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

Subscribe2


 

Reader Interactions

Comments

    Your Comments are too Valuable! But please see that they are related to the above article, and are not off-topic! Cancel reply

    Your email address will not be published. Required fields are marked *

  1. Svaytoslav says

    Hello
    It is possible to use this chip using a differential input and a differential output (additional conditions: minimum gain – up to 6 dB, load – 600ohm headphones.)

    Reply
    • Swagatam says

      Yes, that’s possible…

      Reply
  2. Svaytoslav says

    There is hope! There is an idea to use this amplifier with BT module. Can you provide such a scheme?
    The datasheet does not provide a differential input circuit. The structural diagram shows only the artificial phase shifter inside.
    Thanks.

    Reply
    • Swagatam says

      You can disconnect the second input from the pin2 and use it for the differential input

      Reply
  3. Furgon says

    is it better? waiting for miracle.
    LM386 looks nice if you don’t measure anything. The drawbacks are
    – very low common mode voltage suppression (Vcc)
    – harmonic distortion
    – shape distortion
    – oscillation during the +peak
    – background chip hum
    – detects cellphone radiation, clicking
    – during startup and shutdown, it kicks out 3V pulses to the speaker
    – instability in inverting or none-inverting config.
    – many fake LM386s are on the market, with quite different parameters. Throw it into the garbage.

    Look at the internal guts of LM386. The output driver with Darlington is pain in the a**. If you use transistor output driver with AB class bias 10-20mA and a decent OPAmp, it will work. Miracle chips do not exist. The LM386 is screwed up. A discrete solution is always better.

    Reply

Primary Sidebar

Categories

  • 3-Phase Power (15)
  • 324 IC Circuits (19)
  • 4017 IC Circuits (53)
  • 4060 IC Circuits (25)
  • 555 IC Circuits (98)
  • 741 IC Circuits (19)
  • Amplifiers (58)
  • Arduino Engineering Projects (82)
  • Audio Projects (94)
  • Battery Chargers (82)
  • Car and Motorcycle (94)
  • Datasheets (46)
  • Decorative Lighting (Diwali, Christmas) (33)
  • DIY LED Projects (89)
  • Electronic Components (97)
  • Electronic Devices and Circuit Theory (35)
  • Electronics Tutorial (109)
  • Fish Aquarium (5)
  • Free Energy (35)
  • Fun Projects (11)
  • GSM Projects (9)
  • Health Related (18)
  • Heater Controllers (28)
  • Home Electrical Circuits (101)
  • How to Articles (20)
  • Incubator Related (6)
  • Industrial Electronics (28)
  • Infrared (IR) (40)
  • Inverter Circuits (98)
  • Laser Projects (12)
  • LM317/LM338 (21)
  • LM3915 IC (25)
  • Meters and Testers (63)
  • Mini Projects (171)
  • Motor Controller (66)
  • MPPT (7)
  • Oscillator Circuits (24)
  • PIR (Passive Infrared) (8)
  • Power Electronics (33)
  • Power Supply Circuits (74)
  • Radio Circuits (9)
  • Remote Control (47)
  • Security and Alarm (61)
  • Sensors and Detectors (116)
  • SG3525 IC (5)
  • Simple Circuits (74)
  • SMPS (29)
  • Solar Controllers (61)
  • Timer and Delay Relay (54)
  • TL494 IC (5)
  • Transformerless Power Supply (8)
  • Transmitter Circuits (40)
  • Ultrasonic Projects (14)
  • Water Level Controller (45)

Circuit Calculators

  • AWG to Millimeter Converter
  • Battery Back up Time Calculator
  • Capacitance Reactance Calculator
  • IC 555 Astable Calculator
  • IC 555 Monostable Calculator
  • Inductance Calculator
  • LC Resonance Calculator
  • LM317, LM338, LM396 Calculator
  • Ohm’s Law Calculator
  • Phase Angle Phase Shift Calculator
  • Power Factor (PF) Calculator
  • Reactance Calculator
  • Small Signal Transistor(BJT) and Diode Quick Datasheet
  • Transistor Astable Calculator
  • Transistor base Resistor Calculator
  • Voltage Divider Calculator
  • Wire Current Calculator
  • Zener Diode Calculator

Facebook
Twitter
YouTube
Instagram
My Facebook-Page
Quora

© 2022 · Swagatam Innovations

We use cookies on our website to give you the best experience.
Cookie settingsAccept All
Privacy & Cookies Policy

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Please visit the Privacy Policy Page for more info.
Necessary
Always Enabled
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Non-necessary
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.
SAVE & ACCEPT