This is 20 watt audio amplifier circuit design which use IC LM1875 as main component. This circuit is simple and very easy to built. For stereo channel, you need to build the two same circuits which will amplify the both of audio channels (right and left channel). Dual polarity / symmetrical power supply required for this kind of amplifier.
The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications.
The LM1875 delivers 20 watts into a 4 ohm or 8 ohm load on 25V supplies. By using an 8 ohm load and 30V supplies, over 30 watts of power may be delivered. The amplifier is designed to operate with a minimum of external components. Device overload protection consists of both internal current limit and thermal shutdown.
The LM1875 design takes advantage of advanced circuit techniques and processing to achieve extremely low distortion levels even at high output power levels. Other outstanding features include high gain, fast slew rate and a wide power bandwidth, large output voltage swing, high current capability, and a very wide supply range. The amplifier is internally compensated and stable for gains of 10 or greater.
Download LM1875 datasheet for 20 Watt audio amplifier reference project: