Powerful amplifier on tda7294, assembled according to the itun scheme. Chip amplifier TDA7294: description, datasheet and examples of use Power supply circuit for tda7294

The amplifier, the assembly of which we will describe today, despite its relative simplicity, provides quite high parameters. Of course, "chip" devices have a number of limitations, so bulk amplifiers can provide higher performance. At the same time, the scheme we have chosen has a number of advantages:

• it is quite simple;
• costs less;
• practically does not need adjustment;
• quickly assembled (literally in the evening);
• surpasses many amps from the 70s and 80s in quality, and it is quite enough for most applications (and modern systems up to 300 dollars can be given to her);
• this version of the amplifier is universal (suitable for both beginners and experienced radio amateurs).

In any case, a poorly made and incorrectly tuned amplifier will sound worse than a microchip one. And our task is to make good device. It should be noted that the sound of the described amplifier is very good (if it is properly made and properly powered). There is information that some company produced Hi-End amplifiers on the TDA7294 chip. Believe me, our version will be just as good!

• See the characteristics - what devices can be created based on it

The main parameters of the Hi-Fi amplifier on the TDA7294 chip

We note right away that the microcircuit worked stably for an active load of 2–24 Ohms, for an active resistance of 4 Ohms, with a capacitive load of +/- 15 μF, and also with an inductive load of +/- 1.5 mH. Moreover, on capacitive and inductive loads, the distortions remained small. It is worth saying that the amount of distortion is highly dependent on the power source (especially on a capacitive load).

You can see the measurement results directly in the table below:

Parameter	Meaning	Measurement conditions
Pout.max, W (long-term sinusoidal)	36	Supply voltage + - 22V, Rн = 4 Ohm
Frequency range by level -3 dB	9 Hz–50 kHz	Rн = 8 Ohm, Uout = 4 V
Kg, % (by RMAA 5.5 program)	0,008	Rн = 8 Ohm, Рout = 16 W, f = 1 kHz
Sensitivity, V	0,5	Рout.max = 50 W, Rn = 4 Ohm, Uip = +/-27 V

Hi-Fi amplifier on the TDA7294 chip: diagram and description

Detailed scheme hi-fi amplifier on the chip TDA7294

The circuit of this amplifier is practically a repetition of the switching circuit offered by the manufacturer. And this is no coincidence - who knows better how to turn it on. And for sure there will be no surprises due to non-standard inclusion or mode of operation.

We note right away that you won’t get any 80 watts (and even more so 100 watts) from it. Really 40-60, but it will be honest long-term watts. In a short-term pulse, you can get much more, but this will already be RMPO power, by the way, also honest (80–120 W). In "Chinese" watts, this will be several thousand. If anyone is interested - five thousand. It all depends on the power source.

And do not forget that for a stereo amplifier you need twice as much powerful block nutrition (when calculating according to the proposed program, everything is taken into account automatically).

Important!!! The fuse must be at least primary winding transformer! Remember that high voltage is life-threatening, and a short circuit can cause a fire! And one more thing: you can’t turn on the fuse in the “ground” circuit!

The circuit also works from a pulsed source, but here high requirements are placed on the source itself: low ripples, the ability to deliver current up to 10 amperes without problems, strong “drawdowns” and generation failures. Remember that high-frequency ripples are suppressed by the microcircuit much worse, so the level of distortion can increase by 10-100 times, although everything “seems” to be in order there. A good switching source suitable for Hi-Fi audio is complex and not cheap, so it will often be easier and cheaper to make an "old-fashioned" analog power supply.

Circuit board and amplifier assembly on the TDA7294 chip

The printed circuit board is single-sided and has dimensions of 65x70 mm:

The board is wired taking into account all the requirements for wiring high-quality amplifiers. The entrance is divorced as far as possible from the exit, and enclosed in a "screen" of divided land - input and output. The power tracks ensure maximum efficiency of the filtering capacitors (while the length of the leads of the capacitors C10 and C12 should be minimal). In this experimental board, we installed terminal blocks for connecting input, output, and power. A place for them is provided (capacitor C10 may interfere somewhat), but for stationary structures it is better to solder all these wires, because it is more reliable.

Wide tracks, in addition to low resistance, also have the advantage that it is more difficult to exfoliate when overheated. Yes, and in the manufacture of the "laser-ironing" method, if a 1x1 mm square is not "printed" somewhere, then it's not scary. Still, the conductor will not break. In addition, a wide conductor holds heavy parts better (and a thin one can simply peel off the board).

There is only one jumper on the board. It lies under the pins of the microcircuit, so you need to mount it first, and leave enough space under the pins so that it does not short out.

During installation, the following important components were used:

• 0.12 W resistors (except R9);
• capacitors C9, C10, C12 K73-17 63V;
• capacitors C4 K10-47v 6.8 uF 25V.

We consider the use of expensive "audiophile" parts to be unjustified economically, and cheap "ceramic" elements will give the worst sound (although you can use them, just remember that some of them can withstand a voltage of no more than 16 volts and cannot be used as C7).

Electrolytes will fit any modern. The board shows the polarity of connecting all electrolytic capacitors and the diode. Diode - any low-power rectifier, withstanding reverse voltage at least 50 volts (for example 1N4001-1N4007). It is better not to use high-frequency diodes.

In the corners of the board, there is a place for the holes for the M3 mounting screws. You can fasten the board only to the microcircuit case, but it is still more reliable to grab it with screws.

The microcircuit must be installed on a radiator with an area of ​​at least 350 cm2. More is better. In principle, thermal protection is built into it, but it’s better not to tempt fate. Even if active cooling is assumed, the heatsink should still be quite massive: with pulsed heat release, which is typical for music, heat is more efficiently removed by the heatsink's heat capacity (that is, a large cold piece of iron) than by dissipation into the environment.

The metal case of the microcircuit is connected to the "minus" of the power supply. Hence, there are two ways to install it on a radiator:

1. through an insulating lining. In this case, the radiator can be electrically connected to the housing.
2. Directly, while the radiator is necessarily electrically isolated from the case.

The first option is recommended if you are going to drop metal objects (paper clips, coins, screwdrivers) into the case so that there is no short circuit. In this case, the gasket should be as thin as possible, and the radiator should be larger.

The second option provides better cooling, but requires accuracy (for example, you cannot dismantle the microcircuit when the power is on).

In both cases, you need to use a heat-conducting paste, and in the 1st variant, it must be applied both between the chip body and the gasket, and between the gasket and the heatsink.

PCB in Sprint-Layout 4.0 format, diagram in pdf format and the location of the parts on the board in gif format you will find in the archive below:

Debugging a Hi-Fi amplifier on a TDA7294 chip

As practice shows, 90% of all problems with the equipment is its "improper" quality. That is, having soldered another circuit, and having failed to fix it, the radio amateur puts an end to it, and publicly declares the circuit bad. Therefore, commissioning is the most important (and often the most difficult) stage in the creation of an electronic device.

A properly assembled amplifier does not need to be adjusted. But, since no one guarantees that all parts are absolutely working, you need to be careful when you first turn it on.

The first power-up is carried out without load and with the input signal source turned off (it is better to short the input with a jumper altogether). It would be nice to include fuses of the order of 1A in the power circuit (both in the "plus" and "minus" between the power source and the amplifier itself). Briefly (about 0.5 sec.) We apply the supply voltage and make sure that the current consumed from the source is small (the fuses do not burn out). It is convenient if the source has LED indicators. When disconnected from the mains, the LEDs continue to burn for at least 20 seconds: the filter capacitors are discharged for a long time by a small quiescent current of the microcircuit.

If the current consumed by the microcircuit is large (more than 300 mA), then there can be many reasons:

• Short circuit in installation;
• poor contact in the "ground" wire from the source;
• mixed up "plus" and "minus";
• the pins of the microcircuit touch the jumper;
• microcircuit is faulty;
• capacitors C11, C13 are incorrectly soldered;
• capacitors C10-C13 are faulty.

After making sure that everything is in order with the quiescent current, boldly turn on the power and measure the constant voltage at the output. Its value should not exceed +/- 0.05 V. A large voltage indicates problems with C3 (less often with C4) or with a microcircuit. There were cases when the "inter-ground" resistor was either poorly soldered, or instead of 3 ohms it had a resistance of 3 kOhm. At the same time, the output was a constant of 10–20 volts. By connecting an AC voltmeter to the output, we make sure that the AC voltage at the output is zero (this is best done with the input closed or simply with the input cable not connected, otherwise there will be noise at the output).

The presence of an alternating voltage at the output indicates problems with the microcircuit or circuits C7R9, C3R3R4, R10. Unfortunately, often ordinary testers cannot measure high frequency voltage, which appears during self-excitation (up to 100 kHz), so it is best to use an oscilloscope here.

If everything is in order here, we connect the load, once again we check for the absence of excitation already with the load and that's it - you can listen!

But it's better to do one more test. The fact is that the most vile type of amplifier excitation is “ringing” (when excitation appears only in the presence of a signal, and at a certain amplitude). the main problem in that it is difficult to detect without an oscilloscope and a sound generator (and it is not easy to eliminate it), and the sound deteriorates colossally due to huge intermodulation distortion. By ear, this is usually perceived as a “heavy” sound, that is, without any additional overtones (since the frequency is very high), so the listener does not know that his amplifier is excited. He just listens and decides that the microcircuit is “bad” and “does not sound”. With the correct assembly of the amplifier and a normal power supply, this should not be.

Graphical representation of the “ringing” of the amplifier

However, sometimes such distortions occur, and the C7R9 circuit just fights them. But in a normal microcircuit, everything is fine even in the absence of C7R9. We came across copies of a microcircuit with a ringing. In them, the problem was solved by introducing the C7R9 circuit (which is why we use it, although it is not in the datasheet). If such muck takes place even in the presence of C7R9, then you can try to eliminate it by “playing” with the resistance (it can be reduced to 3 ohms), but we would not recommend using such a microcircuit. This is definitely some kind of marriage, and who knows what else will come out in it.

As we noted above, “ringing” can only be seen on an oscilloscope, and not all radio amateurs have this equipment. Although if you want to be good at radio electronics, try to get hold of such devices or at least use them somewhere. To always receive quality sound, must be checked on the instruments. Remember, ringing is a tricky thing that can ruin a sound in a thousand ways.

You can view another method for assembling a Hi-Fi amplifier on a TDA7294 chip in the video below:

One of the first I assembled an amplifier on the TDA7294 according to the scheme proposed by the manufacturer.

At the same time, the quality of sound reproduction, especially in the high-frequency region, did not suit me very much. On the Internet, my attention was drawn to the LINCOR article posted on the site datagor.ru. The author's rave reviews about the sound of the UMZCH on the TDA7294, assembled according to the voltage-controlled current source circuit (ITUN), intrigued me. As a result, I assembled the UMZCH according to the following scheme.

The scheme works as follows. The signal from the input IN goes through the pass capacitor C1 to the low-resistance arm feedback R1 R3, which, together with the capacitor C2, forms a low-pass filter that prevents the penetration of interference and high-frequency noise into the audio path. Together with resistor R4, the input circuit creates the first segment of the FOS, whose K is equal to 2.34. Further, if it were not for the current sensor R7, the gain of the second circuit would be given by the ratio R5/R6 and would be equal to 45.5. final Ku would be about 100. However, there is still a current sensor in the circuit, and its signal, summing up with the voltage drop across R6, creates a partial OOS for current. With our circuit ratings Ku=15.5.

Characteristics of the amplifier when operating at a load of 4 ohms:

- Operating frequency range (Hz) - 20-20000;

– Supply voltage (V) – ±30;

– Rated input voltage (V) – 0.6;

– Rated output power(W) - 73;

– Input resistance (kΩ) – 9.4;

– THD at 60W, no more than (%) – 0.01.

On the printed circuit board a 12V parametric stabilizer is wired to power service circuits 9 and 10 TDA7294, shown in the figure.

In the “Play!” position, the amplifier is in an unlocked state and is ready to work every second. In the "Mute" position, the input and output stages of the microcircuit are blocked, and its consumption is reduced to the minimum standby currents. Capacitances C11 C12 are doubled compared to stock to provide a longer turn-on delay and prevent speaker clicks even when the power supply capacitors are charged for a long time.

Amplifier details

All resistors, except for R7 and R8, are carbon or metal film 0.125–0.25W, type C1-4, C2-23 or MLT–0.25. Resistor R7 is a 5W wirewound resistor. White SQP resistors in a ceramic case are recommended. R8 - Zobel circuit resistor, carbon, wire or metal film 2W.

C1 - film, the highest quality available, lavsan or polypropylene. K73-17 at 63V will also give a satisfactory result. C2 - ceramic disk or any other type, for example K10-17B. C3 - electrolyte of the highest available quality for a voltage of at least 35 V, C4 C7, C8, C9 - film type K73–17 for 63 V. C5 C6 - electrolytic for a voltage of at least 50 V. C11 C12 - any electrolytic for a voltage of at least 25 V. D1 - any 12 ... 15 V zener diode with a power of at least 0.5 W. Instead of the TDA7294 chip, you can use the TDA7296 ... 7293. In the case of using TDA7296, TDA7295, TDA7293, it is necessary to bite off or bend and not solder the 5th leg of the microcircuit.

Both output terminals of the amplifier are "hot", neither of them is grounded, because. the speaker system is also a feedback link. AC is switched between and .

Below is a board layout with element and wire side views created using the Sprint-Layout_6.0 program.

The article is dedicated to lovers of loud and high-quality music. TDA7294 (TDA7293) is a low-frequency amplifier chip manufactured by the French company THOMSON. The circuit contains field effect transistors, which provides high quality sound and soft sound. simple circuit, few additional elements make the circuit available for manufacturing to any radio amateur. A properly assembled amplifier from serviceable parts starts working immediately and does not need to be adjusted.

The audio frequency power amplifier on the TDA 7294 chip differs from other amplifiers of this class:

• high output power
• wide supply voltage range,
• low percentage of harmonic distortion,
• "soft sound,
• few "mounted" parts,
• low cost.

It can be used in amateur radio audio devices, when modifying amplifiers, acoustic systems, audio equipment devices, etc.

The figure below shows typical circuit diagram power amplifier for one channel.

The TDA7294 chip is a powerful operational amplifier whose gain is set by a negative feedback circuit connected between its output (pin 14 of the chip) and the inverted input (pin 2 of the chip). A direct signal is input (pin 3 of the microcircuit). The circuit consists of resistors R1 and capacitor C1. By changing the values ​​​​of the resistances R1, you can adjust the sensitivity of the amplifier to the parameters of the preamplifier.

Structural diagram of the amplifier on the TDA 7294

Technical characteristics of the TDA7294 chip

Technical characteristics of the TDA7293 chip

Schematic diagram of the amplifier on the TDA7294

To assemble this amplifier, you will need the following parts:

1. Chip TDA7294 (or TDA7293)
2. 0.25 watt resistors
R1 - 680 Ohm
R2, R3, R4 - 22 kOhm
R5 - 10 kOhm
R6 - 47 kOhm
R7 - 15 kOhm
3. Film capacitor, polypropylene:
C1 - 0.74 mkF
4. Electrolytic capacitors:
C2, C3, C4 - 22 mkF 50 volt
C5 - 47 mkF 50 volt
5. Resistor variable dual - 50 kOm

On one chip, you can assemble a mono amplifier. To assemble a stereo amplifier, you need to make two boards. To do this, we multiply all the necessary details by two, except for the dual variable resistor and the PSU. But more on that later.

Amplifier printed circuit board on a TDA 7294 chip

The circuit elements are mounted on a printed circuit board made of one-sided foil fiberglass.

A similar circuit, but a little more elements, mostly capacitors. The turn-on delay circuit is enabled at the “mute” input, pin 10. This is done for a soft, pop-free turn-on of the amplifier.

A microcircuit is installed on the board, in which unused conclusions are removed: 5, 11 and 12. Mount with a wire with a cross section of at least 0.74 mm2. The microcircuit itself must be installed on a radiator with an area of ​​at least 600 cm2. The radiator should not touch the amplifier case as it will have a negative supply voltage. The case itself must be connected to a common wire.

If you use a smaller area of ​​​​the radiator, you must make forced airflow by placing a fan in the amplifier case. The fan is suitable from a computer, with a voltage of 12 volts. The microcircuit itself should be mounted on a heatsink using heat-conducting paste. Do not connect the radiator to live parts, except for the negative power bus. As mentioned above, the metal plate at the back of the microcircuit is connected to the negative power circuit.

Microcircuits for both channels can be installed on one common radiator.

Power supply for the amplifier.

The power supply is a step-down transformer with two windings with a voltage of 25 volts and a current of at least 5 amperes. The voltage on the windings must be the same and the filter capacitors too. Voltage surge must not be allowed. When applying bipolar power to the amplifier, it must be supplied at the same time!

Diodes in the rectifier are better to put ultra-fast, but in principle, conventional ones like D242-246 for a current of at least 10A are also suitable. It is advisable to solder a capacitor with a capacity of 0.01 microfarads in parallel with each diode. You can also use ready-made diode bridges with the same current settings.

Filter capacitors C1 and C3 have a capacitance of 22,000 microfarads for a voltage of 50 volts, capacitors C2 and C4 have a capacitance of 0.1 microfarads.

The supply voltage of 35 volts should only be at a load of 8 ohms, if you have a load of 4 ohms, then the supply voltage must be reduced to 27 volts. In this case, the voltage on the secondary windings of the transformer should be 20 volts.

You can use two identical transformers with a power of 240 watts each. One of them is used to obtain a positive voltage, the second - a negative one. The power of two transformers is 480 watts, which is quite suitable for an amplifier with an output power of 2 x 100 watts.

Transformers TBS 024 220-24 can be replaced by any other transformers with a capacity of at least 200 watts each. As mentioned above, nutrition should be the same - transformers must be the same!!! Voltage on secondary winding each transformer from 24 to 29 volts.

Amplifier circuit increased power on two TDA7294 chips in a bridge circuit.

According to this scheme, four microcircuits are needed for the stereo version.

Amplifier Specifications:

• Maximum output power at a load of 8 ohms (power supply +/- 25V) - 150 W;
• Maximum output power at a load of 16 ohms (power supply +/- 35V) - 170 W;
• Load resistance: 8 - 16 Ohm;
• Coef. harmonic distortion, at max. power 150 watts, e.g. 25V, load 8 Ohm, frequency 1 kHz - 10%;
• Coef. harmonic distortion, at a power of 10-100 watts, e.g. 25V, load 8 Ohm, frequency 1 kHz - 0.01%;
• Coef. harmonic distortion, at a power of 10-120 watts, e.g. 35V, load 16 Ohm, frequency 1 kHz - 0.006%;
• Frequency range (with non-frequency response 1 db) - 50Hz ... 100kHz.

View of the finished amplifier in a wooden case with a transparent plexiglass top cover.

For the amplifier to operate at full power, you need to apply required level signal to the input of the microcircuit, and this is not less than 750mV. If the signal is not enough, then you need to assemble a preamplifier for buildup.

Preamplifier circuit on TDA1524A

Setting up the amplifier

A properly assembled amplifier does not need to be adjusted, but no one guarantees that all the parts are absolutely in good order; when you turn it on for the first time, you need to be careful.

The first power-up is carried out without load and with the input signal source turned off (it is better to short the input with a jumper altogether). It would be nice to include fuses of the order of 1A in the power circuit (both in the "plus" and "minus" between the power source and the amplifier itself). We briefly (~0.5 sec.) apply the supply voltage and make sure that the current consumed from the source is small - the fuses do not burn out. It is convenient if the source has LED indicators - when disconnected from the network, the LEDs continue to burn for at least 20 seconds: the filter capacitors are discharged for a long time by a small quiescent current of the microcircuit.

If the current consumed by the microcircuit is large (more than 300 mA), then there can be many reasons: short circuit in the installation; poor contact in the "ground" wire from the source; mixed up "plus" and "minus"; the pins of the microcircuit touch the jumper; microcircuit is faulty; capacitors C11, C13 are incorrectly soldered; capacitors C10-C13 are faulty.

After making sure that everything is fine with the quiescent current, safely turn on the power and measure the constant voltage at the output. Its value should not exceed + -0.05 V. A large voltage indicates problems with C3 (less often with C4), or with a microcircuit. There were cases when the "inter-ground" resistor was either poorly soldered, or instead of 3 ohms it had a resistance of 3 kOhm. At the same time, the output was a constant of 10 ... 20 volts. By connecting an AC voltmeter to the output, we make sure that the AC voltage at the output is zero (this is best done with the input closed, or simply with the input cable not connected, otherwise there will be noise at the output). The presence of an alternating voltage at the output indicates problems with the microcircuit, or circuits C7R9, C3R3R4, R10. Unfortunately, often ordinary testers cannot measure the high-frequency voltage that appears during self-excitation (up to 100 kHz), so it is best to use an oscilloscope here.

Everything! You can enjoy your favorite music!

Now editorial website will show several versions of the famous low-budget audio power amplifier based on two TDA7294 chips. The amplifier is designed to connect to it two speakers with a power of 150 watts. The circuits and preamplifiers are assembled on the basis of the circuitry common for this m / s, so we will not give them again -.

There is a preamplifier with regulators and a power amplifier. Balanced +/- 40V power supply based on a 2x28V transformer and two 10000uF capacitors. Two mono preamps, running in parallel with an 18V supply from the LM7818, drive the TDA chips. Everything is cooled inside the case by a fan, but due to the heating of the radiators, they were taken out of the case. The power limit comes out to almost 2 x 100W (4 ohms) or 200W into the bridge. Everything fits into the computer's power supply case. The amplifier works stably and without any unpleasant extraneous sounds.

TDA7294 chip parameters

• 70W Continuous Power Output (4 ohm load at +/- 27V)
• Harmonic Distortion - 0.005% (5W, 1kHz)
• Limit voltage - +/- 50 V (recommended 10 - 40 V)

This homemade UMZCH really has a relatively high output power and small size. The cost of the project was in the range of 1000 rubles. The case and the transformer got free of charge.

Photos of ULF design on TDA7294

True, with this transformer, such power will be achievable only at signal peaks. Taking into account the proportions of the power supply and the transformer, it has no more than 100 watts, which is not enough for long-term RMS. But we will not be like the Chinese manufacturers of pocket tape recorders, drawing hundreds of watts of PMPO (maximum peak output power) on them either. In reality, up to 70 watts per channel can be removed from the microcircuit, which in any case is not even bad for a home.

Currently, most devices, such as audio amplifiers, use toroidal transformers (round) because they take up less space, have more power and dissipate the magnetic field to a lesser extent, but unfortunately they have one drawback. When switched on, a so-called current pulse occurs, which can reach a value several times greater than the power of the transformer. The result is blown fuses in electrical network. Moreover, the capacitors in the middle of the amplifier create an additional short circuit at the moment of power-up, which can damage the power terminals and parts.

For all transformers (especially toroids) in the power supply, current delay protection () should be used, since at the moment the transformer is turned on there will be an inrush current several times higher than the rated current, for example: for 500 VA, the rated current is about 2 A, and when turned on, it can reach a value of 12 A.

How does the protection system work? The operation consists in temporarily limiting the current flowing during the turn-on of the transformer, so that no inrush current occurs. After approximately 2 seconds, the relay turns on and the transformer returns to normal operation. The whole circuit is built on a separate printed circuit board, its assembly is very simple.

With TDA7294 it is difficult to get the desired 100 watts. Therefore, a 120 W transformer is quite suitable. With it, a power of the order of 2 x 60W and no more can be achieved.

In general, having played enough with TDA and LM, we recommend looking aside STK4241 or STK4050. They are indeed more powerful and best amplifiers sound. As for LM or TDA, they cannot even be compared with STK in terms of distortion. So if you are going to make a really decent 2 x 100W amplifier, do it on two STK4050s (according to the passport, they will safely issue 200 each). In the process of amateur radio practice, a total of 10 amplifiers were made on STK, and no one let me down.

Pretty simple. Even a person who is not very strong in electrical engineering can repeat it. ULF on this chip will be ideal for use as part of a speaker system for 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 we say about the difference from lamp structures - the dimensions are much smaller.

Not required high voltage to power the anode circuits. Of course, there is heating, as in lamp designs. Therefore, if you plan to use the amplifier for a long time, it is best to install, in addition to an aluminum radiator, at least a small fan for forced airflow. Without it, on the TDA7294 microassembly, the amplifier circuit will work, but there is a high probability of switching to temperature protection.

Why TDA7294?

This chip has been very popular for over 20 years. It has won the trust of radio amateurs, since it has very high characteristics, amplifiers based on it are simple, anyone, even a beginner radio amateur, can repeat the design. The amplifier on the TDA7294 chip (the diagram is given in the article) can be either monophonic or stereophonic. The internal device of the microcircuit consists of an audio frequency amplifier built on this microcircuit belongs to class AB.

Advantages of the microcircuit

Benefits of using a microchip for:

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

2. Approximately 120W into 8 ohms (bridged).

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

4. The microcircuit can be powered from a source constant voltage 10-40 V. But there is a small drawback - you must use a bipolar power supply.

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 is even surprising how it allows you to get such high-quality sound.

The purpose of the pins of the microcircuit

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

Similarly: "10" leg - mute mode, also used when designing an amplifier. "11" and "12" conclusions are not used in the design of audio frequency amplifiers. From the "14" output, the output signal is taken and fed to acoustic system. "13" and "15" pins of the microcircuit are "+" and "-" for connecting the power supply of the output stage. On the TDA7294 chip, the circuit is no different from those proposed in the article, it is only supplemented by which it is connected to the input.

Features of microassembly

When designing an audio frequency amplifier, you need to pay attention to one feature - the power minus, and these are the legs "15" and "8", electrically connected to the microcircuit case. Therefore, it is necessary to isolate it from the heat sink, which in any case will be used in the amplifier. For this purpose it is necessary to use a special thermal pad. If you use a bridge amplifier circuit on the TDA7294, pay attention to the version of the case. It can be vertical or horizontal type. The most common is the version designated as TDA7294V.

Protective functions of the TDA7294 chip

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

Amplifier

Simple, accessible to everyone, and most importantly - cheap. In just a few hours, you can collect very good amplifier audio frequency. And most of the time you will spend on etching the board. The structure of the entire amplifier consists of power and control units, as well as 2 ULF channels. Try to use as few wires as possible in the design of the amplifier. Follow these simple guidelines:

1. A prerequisite is the connection of a power source by wires to each UZCH board.

2. Bundle the power wires. With this, it will be possible to slightly compensate for the magnetic field that is created electric shock. To do this, you need to take all three supply wires - “common”, “minus” and “plus”, with a slight tension weave them into one pigtail.

3. In no case do not use the so-called "earth loops" in the construction. This is the case when a common wire connecting all blocks of the structure closes in a loop. The ground wire must be connected in series, starting from the input further to the UZCH board, and must end at the output connectors. It is extremely important to connect the input circuits with shielded wires in isolation.

Standby and mute control unit

This chip also has muting. It is necessary to control the functions using the conclusions "9" and "10". The mode is turned on if there is no voltage on these legs of the microcircuit, or it is less than one and a half volts. To enable the mode, it is necessary to apply a voltage to the microcircuit legs, the value of which exceeds 3.5 V. In order for the amplifier boards to be controlled simultaneously, which is important for bridge-type circuits, one control unit is assembled for all cascades.

When the amplifier turns on, all the capacitors in the power supply are charged. In the control unit, one capacitor also accumulates a charge. When the maximum possible charge is accumulated, 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 disabled second.