The simple and easy-to-make TDA2822M amplifier

The general integrated amplifier circuit has many peripheral components and requires a large heat sink. The power amplifier circuit introduced in this article is simple and easy to make. The circuit is shown in Figure 5-107. A TDA2822M power amplifier integrated circuit is connected in BTL mode. The peripheral components are only one resistor and two capacitors. No heat sink is required, and the playback effect is satisfactory.

The integrated circuit TDA2822M is an 8-pin dual in-line package. If you can't buy it, you can use TDA2822 instead. The package of TDA2822 is the same as that of TDA2822M. The difference between them is: TDA2822M can work from 3V to 15V, while the maximum working voltage of TDA2822 is only 8V. When using TDA2822, the voltage must be reduced to below 8V. The value of R1 is not restricted, and a 10k carbon film resistor is generally selected. C1 can choose a 0.1uF polyester capacitor, and C2 is a 100uF/160V electrolytic capacitor. Figure 5-108 is its printed circuit board diagram. Because the circuit is simple, the printed circuit board can be made by scraping and polishing with water-abrasive paper or kraft paper dipped in a small amount of water, clean with water, wipe dry, apply a layer of rosin alcohol solution, and solder the components directly to the copper foil surface after drying. After soldering, check that everything is correct. Then, do not connect the speaker first, connect the power supply, and the voltage between the positive and negative output terminals should be less than 0.1V. Connect the speaker, touch the input terminal with your hand, and the speaker should make a loud "buzzing" sound. At this time, you can input the signal for a test sound. No holes need to be drilled on the circuit board.

Note when using: Since this amplifier is directly coupled, the input signal cannot have a DC component. If the input signal has a DC component, a capacitor of about 10uF must be connected in series at the input end to isolate it, otherwise a large DC current will flow through the speaker, causing it to heat up and burn. In practice, if Figure 5-107 is properly modified, the effect will be more ideal. The improved circuit is shown in Figure 5-109. It was found in use that the TDA2822M was hot when the volume was turned up to the maximum, so a heat sink was made for the TDA2822M, as shown in Figure 5-110. The heat sink is made of an aluminum sheet with a thickness of 1mm, a length of 38mm, and a width of 25mm. And 5 to 6 grooves with a length of 10mm and a width of 1mm are opened on the heat sink, and then the heat sink is folded into a "mouth" shape along the dotted line. When installing the heat sink, first put some silicone grease on the TDA2822M (the silicone grease can be obtained by cutting open the 3AX31 or 3AX81 tube shell). Just tie it up with a thin wire as shown in Figure 5-111 (a). It should be noted that the pin number of TDA2822M should be written on the side of the heat sink to avoid mistakes during welding. After adding the heat sink, the heat sink only warms up a little when the volume is turned to the maximum, and the heat dissipation effect is good. This method can also be used for heat dissipation of other small integrated circuits. We use two power amplifier circuits to make a stereo power relay for a walkman to drive two small speakers, and the effect is very good.

Actually, it's not as complicated as you. I just connected the horn, connected the speaker, the sound source, and added 6-12V DC and everything was OK. However, after changing to different sound sources and speakers, I found that 2822 is still OK. It is simple to make and the cost is low. It is much better than the cheap active speakers on the market.