Power Audio Amplifier DMOS 2x100W using two TDA2794

The TDA 7294 of T-MICROELECTRONICS is a monolithic integrated circuit in a `Multiwatt 15` shell designed in principle to be used in amplifiers or class AB in high-fidelity applications such as stereo, active speakers, television receivers, and more. Thanks to the large feed area and the capability to offer a very high current at the outlet, it is thus possible to provide a lot high power at loads of 4Ω or 8Ω, even with a power supply that is not correct stabilized due to a very high discharge of this supply voltage. At the consumer electronics world there is an increasing need for sound amplifiers of very high power and completed in a monolithic shell capable of include, at a low cost, performance, taken from better discrete amplifier constructions data. Work to be built this linear integrated circuit with conventional bipolar technology became extremely difficult due to the phenomenon of the second disruption. The conventional bipolar technology limits its operating range, without the risk of destruction of the circuit and therefore, limits the maximum output power which can initially accept loads with high ohmic resistance.
Power Audio Amplifier DMOS 2x100W using two TDA2794 - schematic

Power Audio Amplifier DMOS 2x100W using two TDA2794 - img1

Power Audio Amplifier DMOS 2x100W using two TDA2794 - img2

Power Audio Amplifier DMOS 2x100W using two TDA2794 - img3

TDA2794 full exploitation operating area, which is not at risk to destroy the circuit, it translates by a similar increase in size of the circuit and a more important complexity of the printed circuit which will be built, due in need of disposal of sophisticated protection circuits. To overcome these difficulties is recommended the use of MOS, which avoids the phenomenon of second decomposition. TDA7294 has however designed with mixed bipolar technology and high voltage MOS, technology, called BCD100. This circuit also has, internally, a function activation with a delay to restore to normal function, fact that simplifies its remote control operation avoiding in this way Parasitic noises.

The basic work in designing an integrated circuit, which implements the work of the operator power amplifier, regardless of technology used, is that of the construction of the exit stage. The solution, which appears as a basic one in figure 2 shows the buffer of the DMOS output of tDA7294. This isolator high power high signal, is capable of receiving currents and levels extremely high voltage maintaining always in an acceptable way a low harmonic distortion and good behavior across the frequency response area. It is also required an accurate control of the resting current. A local loop of linear positive feedback produced by differential amplifier A is used to meet the requirements, previously mentioned, allowing in this way and in a simple and efficient way to define a point for the current.

A correct polarization of the output voltage of the transistors is not sufficient to guarantee the absence of distortion. Although one would have been achieved linearity of the characteristic transfer of the stage, the dynamic behavior of the system will must be taken into account. An important help to maintain the distortion presented by the final stage, as low as possible, is provided by the compensation system, which controls the direct connection of the capacity miller at the amplifier output to introduce an alternating positive path local feedback, including the very stage of the exit.

When designing an integrated power circuit, it must be given special attention attention to the circuits involved with the protection of the accessory against short circuits or the overload conditions of the latter.
Due to the absence of the phenomenon the second split, the full exploitation of the operating zone, which is without risk of destruction for the DMOS power transistors are limited only from the maximum consumption curve, which depends on the duration of the irritations applied.

To take full advantage of the possibilities of power transistors, built-in in these system components protection, includes a conventional circuit protection, without risk of destruction, with a new local sensitive technique temperature stabilization, which dynamically controls the maximum consumption. Plus protection against the overloads described before, in his features component.

PCB file: Click here to download 255 file.PCB file: Click here to download 255 file.

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