MINI STEREO AMPLIFIER (TEA2025)

This mini amplifier is based on the Thomson Type TEA2025. In this 16-pin DIL device hides a stereo amplifier that with a supply voltage of 9 V will provide 1watt output per channel into a 4-ohm loudspeaker. At full output, the input sensitivity is about 25 mVpp. If this is too sensitive, a resistor R may be connected between pin 6 and C7 and between pin 11and C2. The sensitivity then becomes (25+ Y2R) mV, provided R> 1k. Furthermore, the supply voltage may lie between 3 V and 12 V. The operation of the IC cannot be discussed here, but for those interested its internal circuit diagram is reproduced in Fig.

One useful feature of the TEA2025 is that it has a soft-start circuit on board, thus obviating annoying plops in the loudspeaker at switch-on. Construction of the amplifier is fairly simple, but has its peculiarities. First, there is the earth, which in this case should not be of wire, but rather consist of a metal earth plane (if you design your own PCB, this would be of copper). If at all possible, pins 4 and 5 as well as pins 12and 13, should be connected to a (copper) area of not less than 5 cm, The two areas should be connected in a suitable manner, and in such a way that a heat sink is formed under the IC as shown in Fig. This ensures both good heat conduction and a good earth. Moreover, all other connections should, of course, be kept as short as possible. This is particularly important in the case of the supply lines, which should be decoupled by C11as close as possible to the IC. The negative terminal of this capacitor should be soldered direct onto the earth plane; the positive terminal is soldered in the normal manner to pin 16. Finally, the distortion' for a power output of about 0.25W is roughly 0.3 per cent.