8W Amplifier with TDA2003 circuit
The amplifier construction in each channel is based on SGS THOMSON's integrated TDA2003. The integrated has five terminals and its external shape is seen in the figure. Inside it is the circuit of a full audio amplifier.
Its circuit completes with minimal external components and can give power to the loudspeakers. The integrated is designed in such a way that it can lead loads of very low impedance up to 1.6Ω. The power attributed to the speakerphone increases as the charge value decreases.
The relationship of the output power to the load is not linear. The output power output is dependent on the supply voltage on the one hand and on the other hand on the load resistance. Here, it should be noted that increasing the supply voltage also results in an increase in power.
The deformation image for TDA2003 is low and ranges around 0.2%. This price of course may be even lower. Its maximum value may reach 10%. Deformation, as it is known, increases sharply when the amplifier reaches its maximum output power. The percentage of deformation increases from two factors a) depending on the output power (how loudly we listen to the music) and B) in relation to the frequency of the incoming signal.
At the output and in particular the output terminal of the integrated, it can yield high currents up to 3.5A (peak value), while it is characterized by very low cross-over distortion. The interesting feature of the amplifier is that it can withstand "mistreatment". This does not, of course, mean that you have to try to short-circuit any terminal with the grounding of the circuit because there is a fear of destroying the terminal.
Frequency response ranges from 40Hz to 15KHz (-3db) when the output power is 1W and the load is 4Ω. The input impedance is 150KΩ at 1KHz. Current consumption at rest is 45mA and increases in intensity.
The theoretical circuit of the amplifier is shown in the figure. It is based on the TDA2003 that is a stand-alone amplifier. Using two integrated can be a stereo amplifier that will cover many needs. The minimum output power of less than 1W is delivered with a supply voltage of 8V. The amplifier needs two complete ones, one for each channel. For four-tone sound, of course you will need four complete ones.
The printed one in the figure has Posts for two completed and intended for stereo use. When installing components for the left and right channels, we use the same material. The supply of the circuit is made by a simple line. The positive feed line, like the negative one, has a common terminal. If you want security, in line with the positive line can get a common security.
The whole construction can be mounted on a metal chassis, where on one side you will also screw the integrated ones, which for their operation definitely need a heatsink for satisfactory temperature removal. To power the amplifier you will get a transformer 12v. This voltage will be rectified with a bridge and will filter the voltage with an electrolytic 4700μF.
The amplifier can also be powered by the car's electric system or even a stabilized power supply with as much output as 18V. The amplifier construction is relatively simple, as long as you only pay attention to the polarity of the electrolytic and the correct position of the integrated ones.
Start assembly by the resistors and electrolytic ones and finally insert the complete. To test the amplifier, you do not need to install heat sinks, of course, if the power you take is small and the test time does not exceed a few seconds.
R1 = 220Ω
R2 = 2,2Ω
R3 = 1Ω
Rx = 39Ω
C1 = 2,2μF
C2 = 470μF
C3 = 0,1μF
C4 = 1000μF/25V
C5 = 100nF
Cx = 39nF
IC1 = TDA2003
IC2 = TDA2003
SP1 = speaker 4Ω/30W