This is the scheme diagram of 20 Watt stereo audio amplifier which use dual IC TDA2005, one IC for left channel and the another one for right channel. Each IC will give you 20 watt output, so the output will be 2×20 Watt. The supply voltage for this circuit is 8VDC to 18VDC, use regulated power supply for better audio output performance.

Use a good quality transformer (of course it wiil be more expensive) to get less noise. It will be another good way to use a sufficient battery to power the circuit. Keep the supply wires as short as possible. Input source should be isolated from the external noises too. It is recommended to use coaxial cable to connect the input audio.

Bottom PCB Layout:

Top PCB Layout and Component Placement:

20 Watt Stereo Audio Amplifier Technical Data:

• Performance of TDA2005M: (for this circuit); At 14.4 V supply voltage: 2 x 20 watts (stereo) into 4 Ohms.
• Distortion: Approx. 0.2% at 4 Watts into 4 ohm load.
• Frequency Range: Approx. 20 Hz to 22 KHz.
• Input Sensitivity: Approx. maximum 150 mV rms.
• Power supply: + 8 to 18 volts, approx. maximum 3.5 Amps per channel.

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:

LM1875 Datasheet

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