20W Audio Amplifier using LM1875

  • Rajkumar Sharma
  • 31966
  • moderate
  • 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)



  • sandeep

    Can this circuit works on 30 DC and give o/p up 10 to 12 W

    5 years ago
  • Raju

    Can this circuit works for 12VDC and gives O/P of 5W 8ohms?

    3 years ago
    • admin

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

      3 years ago
  • Raju

    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.

    3 years ago
  • admin

    You may find more info on this IC on the datasheet here: http://www.ti.com/lit/ds/symlink/lm1875.pdf and you can also search for general info about audio amplifiers. The IC package is TO-220 and the other components are common types easily available.

    3 years ago
  • Raju

    Thank you,
    can I get this as ready module for my internal testing?

    3 years ago
    • admin

      We are sorry, we don’t sell kits or ready products.

      3 years ago
  • Raju

    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?

    3 years ago

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