TDA2822M Simple low power stereo amplifier

Many people may have heard of the TDA2822 before, but for those who havent, it is a small power amplifier that will drive two channels. It is usually in an 8-pin DIL package, but older versions I have seen are 14-pin or similar (there are datasheets for both variants). For simplicity though, my circuits show schematics for the 8-pin DIL package. The datasheet is here, provided by ST. This article is based along the usage of the TDA2822M variant of the chip series as it is commonly available at my supplier at least. The TDA2822 is similar, but has slightly more pins so is less used. A Few Interesting points: I have seen the TDA2822 used in commercial offerings too, based on a circuit very similar to the schematic shown. An old ghetto Blaster used this chip (the 14-pin version) and for a small old system, its performance is better than many cheap offerings today.

I have also seen this chip in use in PC speakers, a pair I got free when I brought a computer case claimed 120W PMPO. Well I wont lie like they do, this amp is only capable of 700mW per channel from a 6V power supply into 8 ohms (should be over a watt with 12V). This amp can also function well as an amp for headphones, providing 20mW into 32 ohms from 3V. I would have used it for that purpose in my main system, but unfortunately, space was limited and all I could do was run some resistors in series with the output to cut down the volume for headphones. So what have I done with these amps then? Well recently I have rebuilt a pair of speakers I had to be amplified with this amp. The speakers are quite large 4in speakers, but the TDA2822M will provide over a watt into each from the 12V PSU I am using. With built in transformer, these speakers easily impress more then most cheap walkman and PC speakers. Update: I have changed my small stereo speakers from a two TDA7052 amps to one TDA2822M amp.

This is because my TDA7052 circuit eventually failed. I guess this is so because the outputs from the TDA7052 are bridged and the removal and insertion of the 3.5mm plug that I used to connect the other speaker to the one with the amplifier circuit in would short the circuit momentary. The new circuit will make use of the TDA2822Ms non-bridged output which is still capable of nearly as much power (enough for the reason I built the speakers). The other amp I built was brought as a project kit and uses a similar circuit, the advantage of course was I didnt need to build the board. I used this amp in a small (ish) FM radio.

Dont ask how I made a stereo FM radio circuit because the circuit was just re-used from a rather sorry. It does have LW and MW too, but these dont work properly. The speakers are just simple elliptical speakers, but quality is bad at all, although it needs a regulated PSU because that digital clock I put in makes the amp hum if it runs off the same unregulated PSU.

Construction

On the other hand, I would recommend, especially for beginners, that you just buy a simple DC adapter (giving about 12V). This is already made and rectified, and most importantly, safe becausemains electricity is dangerous. Get one with a good current output though, I would say 100mA is the absolute minimum, although this amp runs off a 9V PP3 longer than you would expect. For those who want a bit more volume, get a 12V PSU which will provide 1A or more (although more is probably unnecessary), and connect speakers that are sensitive to it, like those elliptical speakers in my radio, or better. Small low cost speakers (especially 55mm or less) have low sensitivity, as do high quality hi-fi speakers and should be avoided unless they are necessary.

This amp can also be very portable, as before I built the radio, I used the amp in a small pair of Walkman type speakers (that were passive). Only from 3V, there was a lot more volume then having them just passive, I recall people were quite impressed (although as you can guess the tone from the speakers was poor). Extra (simple) parts you may want to add to the schematic could be: 3.5mm jack input socket A power switch Batteries 2.1mm power plug (for external PSUs) - if wired correctly, this should disconnect the batteries when a plug is pushed into the socket. Bridge Version There is a bridge variant of this chip available in the datasheet should it be required. It is smaller still then the stereo version of the chip and should provide output levels similar to or even greater then, the TDA7052.
Again, this circuit is simply taken from the datasheet and you may need to modify it to include a single gang volume control. Please refer to the datasheet for schematics, components their values. Thats about all that can be said about this amp because so many applications are possible from it - it is very cheap too, however if you want that extra power, using two TDA7052 amps is also simple and will give you a little more power. Remember that the TDA7052 amplifiers are bridged and may not be suitable for some situations.

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