Tuesday, February 15, 2022

High Performance 56W Audio Power Amplifier using LM3876 IC with PCB

Fig. 1 - High Performance 56W Audio Power Amplifier using LM3876 IC with PCB

This is a High Performance 56W Audio Power Amplifier, based on the LM3876 Integrated Circuit, with great sound quality, powered by a symmetrical power supply.

The Amplifier responds very well in all audible frequency ranges from 20Hz to 20Khz, and has a minimalistic and very compact design, which makes this amplifier a good choice to be assembled with little difficulty.

LM3876 Integrated Circuit Description

The LM3876 is a high-performance audio power amplifier capable of delivering 56W of continuous average power to an load with 0.1% THD+N from 20Hz–20kHz.

The performance of the LM3876, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe) protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA) SPiKe protection. 

Means that these parts are completely safe-guarded at the output against overvoltage, under-voltage, overloads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks.

The LM3876 maintains an excellent signal-to-noise ratio of greater than 95dB (min) with a typical low noise floor of 2.0μV. It exhibits extremely low THD+N values of 0.06% at the rated output into the rated load over the audio spectrum, and provides exceptional linearity with an IMD (SMPTE) typical rating of 0.004%.


  • 56W Continuous Average Output Power into 8Ω
  • 100W Instantaneous Peak Output Power Capability
  • Signal-to-Noise Ratio ≥ 95 dB(Min)
  • An Input Mute Function
  • Output Protection from a Short to Ground or to the Supplies Via Internal Current Limiting Circuitry
  • Output Over-Voltage Protection against Transients from Inductive Loads
  • Supply Under-Voltage Protection, not Allowing Internal Biasing to Occur when |VEE| + |VCC| ≤ 12V, thus Eliminating Turn-On and Turn-Off Transients
  • 11-Lead TO-220 Package
  • Wide Supply Range 20V - 94V

The Schematic Circuit

In Figure 2 below we have components arrangement of the power amplifier circuit with the LM3876 IC, and as we can see, the difficulty is not extreme. 

Since there are few external components, making the amplifier circuit very simple to assemble, and a technician or hobbyist with medium experience can assemble it without much difficulty. 

Fig. 2 - Schematic Circuit High Performance 56W Audio Power Amplifier using LM3876 IC

It is important to remember to be careful when assembling the circuit, not to invert any component such as capacitor diodes, or even when connecting the symmetrical voltage of the power supply. Not to invert the voltage poles, because the integrated circuit or other components can be damaged.

The coil is formed is a 5uH coil, for those who are going to assemble it, you can assemble it with 10 turns of 18 AWG Wire with a 3/8" air core.

Components List

  • Semiconductors
    • U1 .............. LM3876 Integrated Circuit

  • Resistors
    • R1, R5 ....... 1K resistor (brown, black, red, gold)
    • R2, R3 ....... 18K resistor (brown, gray, orange, gold)
    • R4 .............. 10K resistor (brown, black, orange, gold)
    • R6, R7 ....... 22K resistor (red, red, orange, gold)
    • R8 .............. 100Ω resistor (brown, black, brown, gold)
    • R9 .............. 10Ω / 1W resistor (brown, black, black, gold)
    • RP1 ............ 10K Potentiometer

  • Capacitors
    • C1 ................. 2.2μF Ceramic/Polyester Capacitor
    • C2 ................. 220pF Ceramic/Polyester Capacitor
    • C3 ................. 47 Ceramic/Polyester Capacitor
    • C4, C5 .......... 22μF / 65V Electrolytic Capacitor
    • C6, C7, C8 .... 0.1uF Ceramic/Polyester Capacitor
    • C9, C10 ......... 2.200uF / 65V Electrolytic Capacitor
    • L1 .................. Inductor 5uH *Ver Texto

  • Others
    • P1, P2 ............ Screw Terminal Type 5mm 2-Pin Connector
    • P3 .................. Screw Terminal Type 5mm 3-Pin Connector
    • J1 ....................Set of male connectors 2-Pin (Optional)
    • Other .............. PCB, Wires, Speaker, Heat Sink, etc.

Power Supply

Power is supplied through a 24 VAC transformer with center tape, i.e. [+VAC | GND | -VAC], after rectification the source will supply 35 VDC

It is a standard power supply voltage for this amplifier to work with little heating and little distortion, as it works with a minimum of 18V and a maximum of 84V

The current to power this amplifier is of at least 2A, and if it is going to using in stereo mode, two of these same ones, this current has to be doubled to 4 Amperes

In Figure 3 below, we have a suggestion for a power supply that we use in our projects. In this article, besides having the schematic diagram with the Printed Circuit Board, you will understand how to easily calculate your own Power Supply, with the desired voltage.

You can in the link below:

Fig. 3 - Symmetrical Power Supply for Power Amplifiers

Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 4 - PCB - High Performance 56W Audio Power Amplifier using LM3876 IC

Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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My Best Regards!!!

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