Tuesday, October 7, 2008

20W LM1875 Audio Amplifier

20W LM1875 Audio Amplifier

The LM1875 is a 20W 5-pin audio amplifier chip made by National Semiconductor. It can produce a peak power of 30W, and is designed for applications in which you need a moderate power, high fidelity amplifier.


PCB / Connections:

This PCB is NOT drawn to scale! It is to be used for a preview only. To make your PCB, download the Eagle files and print those!

Build a power supply using the Gainclone Power Supply in the Schematics section, and connect it to the appropriate pads on the PCB. Folow the instructions on the image above to connect the input source, speaker, power supply, and all the components.

As always, test the amp with a cheap speaker that damage to it will not cost much to replace, and once it works properly, go ahead and connect your speakers to it. This amplifier is rated to drive a 4 or 8 ohm speaker. It is reccomended to only power a 4-ohm speaker on a +/-25V power supply. Only use a +/-30V power source to maximize output power with an 8-ohm speaker.


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