20W Audio Amplifier using LM1875

Rajkumar Sharma      http://www.rajkumarsharma.com  
Project tested


20W Audio Amplifier kit is based on LM1875 IC.


  • Power supply – 48 VDC
  • Output – 20 W, 4 Ω
  • Very low distortion (THD – 0.015%), good channel separation and ripple rejection
  • IC built-in thermal, short circuit protections
  • Internal output protection diodes
  • Terminal pins for connecting input
  • Power Battery Terminal (PBT) for easy power supply and speaker connection
  • Power-On LED indicator
  • Heatsink for IC
  • Four mounting holes of 3.2 mm each with nut and stud
  • PCB dimensions 48 mm x 60 mm


schematic (1)

Parts List

parts (1)


8 Response on “20W Audio Amplifier using LM1875

    1. According to the datasheet this audio amplifier can give ~ 6W @ 12V power supply input on a 8ohm load. So this is yes.

  1. Hi, Thank you for the reply,
    I am new to this audio amplifier designs, can you tell me that is there any calculations for getting these values? As I was thinking to use the same circuit for making the audio amplifier.

    Also, can you send me the package details of the components used in your circuits so that it will be helpful for me to choose the right components.

  2. The out loudness is very low, is there any changes I can make to increase the volume with same 12VDC single supply? Also there is noise distortions, how can I reduce it?

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