10-Watt Audio Amplifier using LM1875

By Raj K. Gorkhali

16248
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Here is a simple 10-watt audio amplifier using IC LM1875. The IC has five pins and can deliver a maximum of 18-watt output power depending upon the supply voltage and load. The author’s prototype is shown in Fig. 1.

Author’s prototype
Fig. 1: Author’s prototype

Circuit and working

The circuit diagram of the audio amplifier is shown in Fig. 2. It is built around popular amplifier LM1875 (IC1), an 8-ohm, 10-watt speaker (LS1) and a few other components.
Connect the audio input from your mobile/laptop/PC to CON1. Connect 15V battery and switch on S1. You should hear amplified sound in speaker LS1.

Circuit diagram of the simple 10-watt audio amplifier using LM1875
Fig. 2: Circuit diagram of the simple 10-watt audio amplifier using LM1875

Construction and testing

Use a 25-watt soldering iron for soldering LM1875 and other components. A 2-pin connector should be used for input and output connections to make the prototype safe and clean. Use a suitable heat-sink for LM1875 to prevent its overheating.

An actual-size, PCB layout for the amplifier is shown in Fig. 3 and its components layout in Fig. 4. After assembling the circuit on the PCB, enclose it in a suitable box. Fix LS1 on the rear side of the box.

PCB layout of the audio amplifier
Fig. 3: PCB layout of the audio amplifier
Components layout for the PCB
Fig. 4: Components layout for the PCB

Download PCB and component layout PDFs: click here

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For testing the circuit, connect a 6V battery to this circuit along with an 8-ohm, 10-watt speaker.

Take a metal screwdriver and gently touch at the input terminal. If your prototype is working, you will hear a humming sound from the speaker. You may connect a 100-kilo-ohm potmeter between audio input and ground and middle pin of potmeter to pin 1 for volume control. Your circuit is now ready to use.

You can use the power supply from a 5V to 15V battery, which will give you clear and noise-free audio signal output.


Raj K. Gorkhali is a regular contributor to EFY. His interests include designing electronics circuits

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4 COMMENTS

  1. This circuit is not working. The circuit in the datasheet has a voltage divider consisting of two resistors but here only one resistor is connected at input pin 1. Also, a single supply configuration won’t g higher power even at 2 Ampere supply.

  2. This circuit is not working as there should be a voltage divider network at pin 1 of the IC. Also, it can’t give 10 Watts at Single supply of 15 Volts since it’s designed to work properly on Split supply. I have constructed the circuit according to datasheet and it gives only 2 Watts max at 22 Volts, 2 Amp transformer

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