TDA7294: amplifier circuit. Bridge amplifier circuit for TDA7294

On the TDA7294 chip, the amplifier circuit is quite simple, it can be repeated even by a person who is not very strong in electrical engineering. ULF on this chip will be ideal for use as a part of the speaker system for a home computer, TV, cinema. Its advantage is that fine tuning and tuning is not required, as is the case with transistor amplifiers. And what can one say about the difference from lamp designs - the dimensions are much smaller.

No high voltage is required to supply the anode circuits. Of course, there is heating, as in the lamp constructions. Therefore, in the event that it is planned to use the amplifier for a long time, it is best to install, in addition to an aluminum radiator, even at least a small fan for forced blowing. Without it, on the TDA7294 microassembly, the amplifier circuit will work, but the probability of transition to temperature protection is high.

Why TDA7294?

This chip has been very popular for more than 20 years. It has gained the trust of radio amateurs, since it has very high characteristics, the amplifiers based on it are simple, anyone can even repeat the design, even a novice ham radio. The amplifier on the TDA7294 chip (the scheme is given in the article) can be both monophonic and stereophonic. The internal arrangement of the chip consists of field-effect transistors. The audio frequency amplifier built on this chip belongs to the class AB.

Advantages of the chip

Advantages of using a chip for audio amplifiers:

1. Very high output power. About 70 watts, if the load has a resistance of 4 ohms. In this case, the usual scheme for switching on the microcircuit is used.

2. Approximately 120 watts at a load of 8 ohms (in the bridge circuit).

3. Very low level of extraneous noise, distortion inessential, reproducible frequencies lie in a range completely perceived by the human ear - from 20 Hz to 20 kHz.

4. Power chip can be made from a constant voltage source 10-40 V. But there is a small drawback - it is necessary to use a bipolar power source.

It is worth paying attention to one feature - the distortion factor does not exceed 1%. On the TDA7294 microassembly, the power amplifier circuit is so simple that it's even amazing how it produces such a quality sound.

Pin Assignments of the IC

And now more in detail about what conclusions are available from TDA7294. The first leg is the "signal ground", it is connected to the common wire of the whole structure. Conclusions "2" and "3" are inverting and non-inverting inputs, respectively. The "4" pin is also the "signal ground" connected to the common wire. The fifth leg in the audio frequency amplifiers is not used. "6" leg is a volt-additive, an electrolytic capacitor is connected to it. "7" and "8" conclusions - plus and minus supply of the input stages, respectively. Leg "9" - standby mode, used in the control unit.

Similarly: "10" foot - mute mode, is also used in the design of the amplifier control unit. "11" and "12" conclusions are not used in the design of audio amplifiers. With the "14" pin, the output signal is removed and fed to the speaker system. The "13" and "15" pins of the IC are "+" and "-" for powering the output stage. On the TDA7294 chip, the amplifier circuit for the subwoofer does not differ from the ones proposed in the article, it is supplemented only with a low-pass filter that connects to the input.

Features of microassembly

When designing an audio frequency amplifier, one should pay attention to one feature - minus the supply, and these are the legs "15" and "8", electrically connected to the housing of the chip. Therefore, it is necessary to isolate it from the radiator, which in any case will be used in the amplifier. For this purpose, a special thermal padding must be used. If a bridge circuit is used for the TDA7294, pay attention to the housing version. It can be either vertical or horizontal type. The most common is the version, designated as TDA7294V.

Protective functions of the chip TDA7294

The chip provides several types of protection, in particular, from the drop in supply voltage. If the supply voltage changes suddenly, the microcircuit will go into protection mode, therefore, there will be no electrical damage. The output stage also has protection against overloads and short circuits. If the case of the device heats up to a temperature of 145 degrees, the sound is muted. When it reaches 150 degrees, it goes into standby mode. All conclusions of the TDA7294 chip are protected from electrostatics.

Amplifier

Simple, affordable for everyone, and most importantly - cheap. Just a few hours you can assemble a very good audio amplifier. And most of the time you spend on it to effect etching of the board. The structure of the entire amplifier consists of power and control units, as well as 2 channels of ULF. Try to use as few wires as possible in the design of the amplifier. Follow simple recommendations:

1. A prerequisite is the connection of the power supply to the wires to each UHF board.

2. Connect the supply wires to the harness. With the help of this it will be possible to slightly compensate the magnetic field, which is created by electric current. For this, it is necessary to take all three supply wires - "common", "minus" and "plus", with a small tension to weave them into one pigtail.

3. Do not use the so-called "earth loops" in the construction. This is the case when the common wire connecting all the structural units closes into a loop. The ground wire must be connected in series, starting from the input volume controls, then to the UHF board, and terminated at the output connectors. It is extremely important to connect the input circuits with shielded wires in isolation.

Waiting and Muting Control Unit

This chip has a standby and mute mode. The functions must be controlled using the "9" and "10" outputs. The mode is enabled if there are no voltages on these legs, or less than one and a half volts. To enable the mode, it is necessary to apply voltage to the legs of the chip, the value of which exceeds 3.5 V. To control the boards of the amplifier occurred simultaneously, which is important for circuits constructed by the type of bridge, one control unit is assembled for all stages.

When the amplifier is turned on, all capacitors are charged in the power supply. In the control unit, one capacitor also accumulates a charge. When accumulating the maximum possible charge, the standby mode is turned off. The second capacitor used in the control unit is responsible for the operation of the mute mode. It charges a little later, so the mute mode is turned off by the second one.