Quite simple, even a person who is not very strong in electrical engineering can repeat it. The ULF on this chip will be ideal for use as part of an acoustic system for a home computer, TV, or cinema. Its advantage is that it does not require fine adjustment and tuning, as is the case with transistor amplifiers. And what can we say about the difference from lamp designs - the dimensions are much smaller.

No high voltage is required 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, the amplifier circuit on the TDA7294 microassembly will work, but there is a high probability of it going into temperature protection.

Why TDA7294?

This chip has been very popular for more than 20 years. It has won the trust of radio amateurs, since it has very high characteristics, the amplifiers based on it are simple, and anyone, even a novice radio amateur, can repeat the design. The amplifier on the TDA7294 chip (the circuit is shown in the article) can be either monophonic or stereophonic. The internal structure of the microcircuit consists of: An audio amplifier built on this microcircuit belongs to class AB.

Advantages of the microcircuit

Advantages of using a microcircuit for:

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

2. About 120 W at 8 ohms (bridged).

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

4. The microcircuit can be powered from a DC voltage source of 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 coefficient does not exceed 1%. On the TDA7294 microassembly, the power amplifier circuit is so simple that it’s even surprising how it allows you to get such high-quality sound.

Purpose of the microcircuit pins

And now in more detail about what conclusions the TDA7294 has. The first leg is the “signal ground”, connected to the common wire of the entire structure. Pins “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 is not used in audio amplifiers. “6” leg is a volt add-on; an electrolytic capacitor is connected to it. “7” and “8” pins are plus and minus power supply for the input stages, respectively. Leg “9” – standby mode, used in the control unit.

Similarly: “10” leg - muting mode, also used when designing an amplifier. “11” and “12” pins are not used in the design of audio amplifiers. The output signal is taken from the “14” pin and supplied to the speaker system. “13” and “15” pins of the microcircuit are “+” and “-” for connecting the power to the output stage. On the TDA7294 chip, the circuit is no different from those proposed in the article, it is supplemented only by the circuit that is connected to the input.

Features of microassembly

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

Protective functions of the TDA7294 chip

The microcircuit provides several types of protection, in particular, against supply voltage drop. 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 overload and short circuit. If the device body heats up to a temperature of 145 degrees, the sound turns off. When 150 degrees is reached, it switches to 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 assemble a very good audio amplifier. Moreover, you will spend most of the time 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 amplifier design. Follow simple recommendations:

1. A prerequisite is to connect the power source with wires to each ultrasonic circuit board.

2. Tie the power wires into a bundle. With this, you can slightly compensate for the magnetic field created by electric current. To do this, you need to take all three power wires - “common”, “minus” and “plus”, and with a little tension weave them into one braid.

3. Under no circumstances use so-called “earth loops” in the design. This is the case when the common wire connecting all the blocks of the structure is closed into a loop. The ground wire must be connected sequentially, starting from the input terminals further to the ultrasonic circuit board, and ending at the output connectors. It is extremely important to connect the input circuits using shielded and insulated wires.

Control unit for standby and muting modes

This chip also has muting. Functions must be controlled using pins “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 legs of the microcircuit, 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 stages.

When the amplifier is turned on, all the capacitors in the power supply are charged. There is also one capacitor in the control unit that stores 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 muting mode. It charges a little later, so the mute mode turns off second.

TDA 2003 chip amplifier

Everyone is familiar with the mono amplifier circuit on the TDA 2003 microcircuit. It is used in various radio equipment: televisions, computer speakers, car radios, etc. This amplifier microcircuit is powered by a voltage of 8 - 18 volts, the current consumption at rest is -50 mA, the maximum is 3A. Output power (Up=14V): - RL=4.0 Ohm - 6 W - RL=3.2 Ohm - 7.5 W - RL=2.0 Ohm - 10 W Analogue - K174UN14.

A very simple ULF on two microcircuits and two transistors

The amplifier develops output power up to 25 watts per channel. Can operate on a load of 3-10 ohms. In general, a good analog HI-FI amplifier THD no more than 0.03%

Simple bass amplifier

Amplifier specifications:

Nominal frequency range, Hz...................63...12500. Rated input voltage, V.................................... 0.25. Rated input power, W, at a load with a resistance of 4 Ohms with a harmonic coefficient of no more than 1% .................................. 2.

UMZCH on TDA2005

A simple UMZCH on a cheap TDA2005 chip. Develops power up to 18W, works well from a car on-board network and from a laboratory source. It doesn’t require any setup - you just need to assemble it correctly, and don’t forget about the radiator. The print is given “in a mirror” under a “laser iron”. Capacitors for voltage not lower than the supply voltage. I hope it is useful to someone.

Powerful ULF for audio center

When making an audio center yourself or upgrading an existing one, or developing an amplifier for a home theater, you may need a compact and powerful UMZCH module. An amplifier made on the basis of the TDA 7294 microcircuit is very convenient in this sense; such advantages of the microcircuit as high output power, a wide range of supply voltage and

low level of harmonic distortion, combined with a very affordable price, make it attractive to use

amplifier in many home-made audio equipment designs, as well as during the repair and modernization of industrially produced ULF equipment.

Specifications:

2. Rated supply voltage +30V.

3. The maximum output power at a rated supply voltage at a load of 4 Ot is 100W.

4. Input impedance 22 kOt.

5. Sensitivity 750 mV.

6. Harmonic distortion coefficient at 60W power, no more than 0.5%.

7. Load resistance from 4 to 8 Ot.

By selecting R1 or R2 you can adjust the sensitivity of the power amplifier. The amplifier is turned on in a “soft way”

using switch S1. There is one switch S1 for both channels; if there are two channels, there simply won’t be a second channel in the circuit

resistors R7 and R6, and the connection point of R4 and R5 is connected to a similar point of the other channel.

Pins 5, 12 and 11 of the microcircuit are not used, so as not to complicate the board layout; they are not connected anywhere. There aren't even holes for them. They need to be folded up or removed. A radiator is extremely necessary, since during operation the microcircuit heats up very quickly and noticeably.

You cannot turn on the amplifier without a radiator, even for a short time. With a power of about 100W, the surface area of ​​the radiator should be at least 500 cm2. You can also use a radiator with a smaller surface, but ensure its forced airflow using a fan, for example, from a power source

personal computer

It is not necessary to isolate the heatsink from the microcircuit, but only

if it is not connected to the common power wire or other live parts other than the negative power bus. The fact is that the TDA7294 has a negative power circuit in contact with the radiator plate.

ULF on TDA7294 chip

TDA7294- the brainchild of SGS-THOMSON Microelectronics, this microcircuit is an AB class low-frequency amplifier, and is built on field-effect transistors. It is almost impossible to disable it, in other words, to burn it, it has protection against short circuits and overheating.

The advantages of the TDA7294 include the following:

output power 70W for a load with a resistance of 4 Ohms, with distortion of 0.3-0.8%;

Mute and Stand-By functions;

low noise level, low distortion, frequency range 20-20000Hz, wide operating voltage range - ±10 - ±40V.

Powerful bridge ULF 4x40 W on TDA8571J

The ULF is made on an integrated circuit TDA8571J (DA1). This IC is a class B ULF and is installed in car audio devices to obtain a high-quality output music signal of medium power. The microcircuit contains four identical bridge amplifiers developing power up to 40 W into a 4 Ohm load.

Amplifier Specifications

• operating voltage Upab = 14.4V (8-18V);
• nominal resistance Rн = 4 Ohm;
• frequency range F = 20... 20000 Hz

By closing the SW1 contacts, the microcircuit is transferred from standby mode to operating mode and vice versa.

A characteristic feature of this microcircuit is the presence of diagnostic output 9, which in turn made it possible to display the following emergency situations:

IC overload

IC overheating

Short circuit in load

Particular attention should be paid to connecting the amplifier to the power source: the IC is extremely sensitive to the supply voltage - a maximum of 18 V. Reversing the polarity of the supply voltage leads to failure of the IC.

The amplifier chip must be installed on the heat sink. As a radiator, you can use the metal case or chassis of the device into which the ULF is installed. During installation, it is recommended to use heat-conducting paste type KTP-8.

Instead of transistor VT1, KT3102, KT315 and the like are quite suitable; instead of VT2 there will be KT3107, KT361; LED - any

Updated: 04/27/2016

An excellent amplifier for home can be assembled using the TDA7294 chip. If you are not strong in electronics, then such an amplifier is an ideal option; it does not require fine tuning and debugging like a transistor amplifier and is easy to build, unlike a tube amplifier.

The TDA7294 microcircuit has been in production for 20 years and has still not lost its relevance and is still in demand among radio amateurs. For a novice radio amateur, this article will be a good help in getting to know integrated audio amplifiers.

In this article I will try to describe in detail the design of the amplifier on the TDA7294. I will focus on a stereo amplifier assembled according to the usual circuit (1 microcircuit per channel) and will briefly talk about the bridge circuit (2 microcircuits per channel).

TDA7294 chip and its features

TDA7294 is the brainchild of SGS-THOMSON Microelectronics, this chip is an AB class low-frequency amplifier, and is built on field-effect transistors.

The advantages of the TDA7294 include the following:

• output power, with distortion 0.3–0.8%:
  • 70 W for 4 ohm load, conventional circuit;
  • 120 W for 8 ohm load, bridge circuit;
• Mute function and Stand-By function;
• low noise level, low distortion, frequency range 20–20000 Hz, wide operating voltage range - ±10–40 V.

Specifications

Technical characteristics of the TDA7294 chip
Parameter	Conditions	Minimum	Typical	Maximum	Units
Supply voltage		±10		±40	IN
Frequency range	Signal 3 db Output power 1W	20-20000			Hz
Long-term output power (RMS)	harmonic coefficient 0.5%: Up = ±35 V, Rн = 8 Ohm Up = ±31 V, Rн = 6 Ohm Up = ±27 V, Rн = 4 Ohm	60 60 60	70 70 70		W
Peak music output power (RMS), duration 1 sec.	harmonic factor 10%: Up = ±38 V, Rн = 8 Ohm Up = ±33 V, Rн = 6 Ohm Up = ±29 V, Rн = 4 Ohm		100 100 100		W
Total harmonic distortion	Po = 5W; 1kHz Po = 0.1–50W; 20–20000Hz		0,005	0,1	%
	Up = ±27 V, Rн = 4 Ohm: Po = 5W; 1kHz Po = 0.1–50W; 20–20000Hz		0,01	0,1	%
Protection response temperature		145			°C
Quiescent current		20	30	60	mA
Input impedance		100			kOhm
Voltage Gain		24	30	40	dB
Peak output current		10			A
Operating temperature range		0		70	°C
Case thermal resistance				1,5	°C/W

Pin assignment

Pin assignment of the TDA7294 chip
IC output	Designation	Purpose	Connection
1	Stby-GND	"Signal Ground"	"General"
2	In-	Inverting input	Feedback
3	In+	Non-inverting input	Audio input via coupling capacitor
4	In+Mute	"Signal Ground"	"General"
5	N.C.	Not used	–
6	Bootstrap	"Voltage boost"	Capacitor
7	+Vs	Input stage power supply (+)
8	-Vs	Input stage power supply (-)
9	Stby	Standby mode	Control block
10	Mute	Mute mode
11	N.C.	Not used	–
12	N.C.	Not used	–
13	+PwVs	Output stage power supply (+)	Positive terminal (+) of the power supply
14	Out	Exit	Audio output
15	-PwVs	Output stage power supply (-)	Negative terminal (-) of the power supply

Note. The microcircuit body is connected to the power supply negative (pins 8 and 15). Do not forget about insulating the radiator from the amplifier body or insulating the microcircuit from the radiator by installing it through a thermal pad.

I would also like to note that in my circuit (as well as in the datasheet) there is no separation of input and output lands. Therefore, in the description and in the diagram, the definitions of “general”, “ground”, “housing”, GND should be perceived as concepts of the same sense.

The difference is in the cases

The TDA7294 chip is available in two types - V (vertical) and HS (horizontal). The TDA7294V, having a classic vertical body design, was the first to roll off the production line and is still the most common and affordable.

Complex of protections

The TDA7294 chip has a number of protections:

• protection against power surges;
• protection of the output stage from short circuit or overload;
• thermal protection. When the microcircuit heats up to 145 °C, the mute mode is activated, and at 150 °C the standby mode is activated;
• protection of microcircuit pins from electrostatic discharges.

Power amplifier on TDA7294

A minimum of parts in the harness, a simple printed circuit board, patience and known good parts will allow you to easily assemble an inexpensive TDA7294 UMZCH with clear sound and good power for home use.

You can connect this amplifier directly to the line output of your computer sound card, because The nominal input voltage of the amplifier is 700 mV. And the nominal voltage level of the linear output of the sound card is regulated within 0.7–2 V.

Amplifier block diagram

The diagram shows a version of a stereo amplifier. The structure of the amplifier using a bridge circuit is similar - there are also two boards with TDA7294.

• A0. power unit
• A1. Control unit for Mute and Stand-By modes
• A2. UMZCH (left channel)
• A3. UMZCH (right channel)

Pay attention to the connection of the blocks. Improper wiring inside the amplifier may cause additional interference. To minimize noise as much as possible, follow several rules:

1. Power must be supplied to each amplifier board using a separate harness.
2. The power wires must be twisted into a braid (harness). This will compensate for the magnetic fields created by the current flowing through the conductors. We take three wires (“+”, “-”, “Common”) and weave them into a pigtail with a slight tension.
3. Avoid ground loops. This is a situation where a common conductor, connecting blocks, forms a closed circuit (loop). The connection of the common wire must go in series from the input connectors to the volume control, from it to the UMZCH board and then to the output connectors. It is advisable to use connectors isolated from the housing. And for input circuits there are also shielded and insulated wires.

List of parts for TDA7294 power supply:

When purchasing a transformer, please note that the effective voltage value is written on it - U D, and by measuring it with a voltmeter you will also see the effective value. At the output after the rectifier bridge, the capacitors are charged to the amplitude voltage - U A. The amplitude and effective voltages are related by the following relationship:

U A = 1.41 × U D

According to the characteristics of the TDA7294, for a load with a resistance of 4 Ohms, the optimal supply voltage is ±27 volts (U A). The output power at this voltage will be 70 W. This is the optimal power for the TDA7294 - the distortion level will be 0.3–0.8%. There is no point in increasing the power supply to increase power because... the level of distortion increases like an avalanche (see graph).

We calculate the required voltage of each secondary winding of the transformer:

U D = 27 ÷ 1.41 ≈ 19 V

I have a transformer with two secondary windings, with a voltage of 20 volts on each winding. Therefore, in the diagram I designated the power terminals as ± 28 V.

To obtain 70 W per channel, taking into account the efficiency of the microcircuit of 66%, we calculate the power of the transformer:

P = 70 ÷ 0.66 ≈ 106 VA

Accordingly, for two TDA7294 this is 212 VA. The nearest standard transformer, with a margin, will be 250 VA.

It is appropriate to state here that the power of the transformer is calculated for a pure sinusoidal signal; corrections are possible for a real musical sound. So, Igor Rogov claims that for a 50 W amplifier, a 60 VA transformer will be sufficient.

The high-voltage part of the power supply (before the transformer) is assembled on a 35x20 mm printed circuit board; it can also be mounted:

The low-voltage part (A0 according to the structural diagram) is assembled on a 115x45 mm printed circuit board:

All amplifier boards are available in one.

This power supply for the TDA7294 is designed for two chips. For a larger number of microcircuits, you will have to replace the diode bridge and increase the capacitor capacity, which will entail a change in the dimensions of the board.

Control unit for Mute and Stand-By modes

The TDA7294 chip has a Stand-By mode and a Mute mode. These functions are controlled through pins 9 and 10, respectively. The modes will be enabled as long as there is no voltage on these pins or it is less than +1.5 V. To “wake up” the microcircuit, it is enough to apply a voltage greater than +3.5 V to pins 9 and 10.

To simultaneously control all UMZCH boards (especially important for bridge circuits) and save radio components, there is a reason to assemble a separate control unit (A1 according to the block diagram):

Parts list for control box:

• Diode (VD1). 1N4001 or similar.
• Capacitors (C1, C2). Polar electrolytic, domestic K50-35 or imported, 47 uF 25 V.
• Resistors (R1–R4). Ordinary low-power ones.

The printed circuit board of the block has dimensions of 35×32 mm:

The control unit's task is to ensure silent switching on and off of the amplifier using the Stand-By and Mute modes.

The operating principle is as follows. When the amplifier is turned on, along with the capacitors of the power supply, capacitor C2 of the control unit is also charged. Once it is charged, Stand-By mode will turn off. It takes a little longer for capacitor C1 to charge, so Mute mode will turn off second.

When the amplifier is disconnected from the network, capacitor C1 discharges first through diode VD1 and turns on the Mute mode. Then capacitor C2 discharges and sets the Stand-By mode. The microcircuit becomes silent when the power supply capacitors have a charge of about 12 volts, so no clicks or other sounds are heard.

Amplifier based on TDA7294 according to the usual circuit

The microcircuit's connection circuit is non-inverting, the concept corresponds to the original one from the datasheet, only the component values ​​have been changed to improve the sound characteristics.

Parts List:

1. Capacitors:
   • C1. Film, 0.33–1 µF.
   • C2, C3. Electrolytic, 100-470 µF 50 V.
   • C4, C5. Film, 0.68 µF 63 V.
   • C6, C7. Electrolytic, 1000 µF 50 V.
2. Resistors:
   • R1. Variable dual with linear characteristic.
   • R2–R4. Ordinary low-power ones.

Resistor R1 is double because stereo amplifier. Resistance of no more than 50 kOhm with a linear rather than logarithmic characteristic for smooth volume control.

Circuit R2C1 is a high-pass filter (HPF) that suppresses frequencies below 7 Hz without passing them to the amplifier input. Resistors R2 and R4 must be equal to ensure stable operation of the amplifier.

Resistors R3 and R4 organize a negative feedback circuit (NFC) and set the gain:

Ku = R4 ÷ R3 = 22 ÷ 0.68 ≈ 32 dB

According to the datasheet, the gain should be in the range of 24–40 dB. If it is less, the microcircuit will self-excite; if it is more, distortion will increase.

Capacitor C2 is involved in the OOS circuit; it is better to take one with a larger capacitance to reduce its effect on low frequencies. Capacitor C3 provides an increase in the supply voltage of the output stages of the microcircuit - “voltage boost”. Capacitors C4, C5 eliminate noise introduced by wires, and C6, C7 supplement the filter capacity of the power supply. All amplifier capacitors, except C1, must have a voltage reserve, so we take 50 V.

The amplifier's printed circuit board is single-sided, quite compact - 55x70 mm. When developing it, the goal was to separate the “ground” with a star, ensure versatility and at the same time maintain minimal dimensions. I think this is one of the smallest boards for TDA7294. This board is designed for installation of one microcircuit. For the stereo option, accordingly, you will need two boards. They can be installed side by side or one above the other like mine. I’ll tell you more about versatility a little later.

The radiator, as you can see, is indicated on one board, and the second, similar one, is attached to it from above. Photos will be a little further.

Amplifier based on TDA7294 using a bridge circuit

A bridge circuit is a pairing of two conventional amplifiers with some adjustments. This circuit solution is designed for connecting acoustics with a resistance of not 4, but 8 ohms! Acoustics are connected between the amplifier outputs.

There are only two differences from the usual scheme:

• the input capacitor C1 of the second amplifier is connected to ground;
• added feedback resistor (R5).

The printed circuit board is also a combination of amplifiers according to the usual circuit. Board size – 110×70 mm.

Universal board for TDA7294

As you have already noticed, the above boards are essentially the same. The following version of the printed circuit board fully confirms the versatility. On this board you can assemble a 2x70 W stereo amplifier (regular circuit) or a 1x120 W mono amplifier (bridged). Board size – 110×70 mm.

Note. To use this board in a bridge version, you need to install resistor R5 and install jumper S1 in a horizontal position. In the figure, these elements are shown as dotted lines.

For a conventional circuit, resistor R5 is not needed, and the jumper must be installed in a vertical position.

Assembly and adjustment

Assembling the amplifier will not pose any particular difficulties. The amplifier does not require any adjustment as such and will work immediately, provided that everything is assembled correctly and the microcircuit is not defective.

Before first use:

1. Make sure the radio components are installed correctly.
2. Check that the power wires are connected correctly, do not forget that on my amplifier board the ground is not centered between plus and minus, but on the edge.
3. Make sure that the microcircuits are isolated from the radiator; if not, then check that the radiator is not in contact with ground.
4. Apply power to each amplifier in turn, so there is a chance you won’t burn out all the TDA7294 at once.

First start:

1. We do not connect the load (acoustics).
2. We connect the amplifier inputs to ground (connect X1 to X2 on the amplifier board).
3. We serve food. If everything is fine with the fuses in the power supply and nothing smokes, then the launch was a success.
4. Using a multimeter, we check the absence of direct and alternating voltage at the output of the amplifier. A slight constant voltage is allowed, no more than ±0.05 volts.
5. Turn off the power and check the chip body for heating. Be careful, the capacitors in the power supply take a long time to discharge.
6. We send a sound signal through a variable resistor (R1 according to the diagram). Turn on the amplifier. The sound should appear with a slight delay, and disappear immediately when turned off; this characterizes the operation of the control unit (A1).

Conclusion

I hope this article will help you build a high-quality amplifier using the TDA7294. Finally, I present a few photos of the assembly process, do not pay attention to the quality of the board, the old PCB is unevenly etched. Based on the assembly results, some edits were made, so the boards in the .lay file are slightly different from the boards in the photographs.

The amplifier was made for a good friend, he came up with and implemented such an original housing. Photos of the assembled stereo amplifier on the TDA7294:

On a note: All printed circuit boards are collected in one file. To switch between “signatures”, click on the tabs as shown in the figure.

list of files

In this article I will tell you about a microcircuit such as TDA1514A

Introduction

Let me start with something sad... At the moment, production of the microcircuit has been discontinued... But this does not mean that it is now “worth its weight in gold”, no. You can get it in almost any radio store or radio market for 100 - 500 rubles. Agree, a little expensive, but the price is absolutely fair! By the way, on global Internet sites such as these they are much cheaper...

The microcircuit is characterized by a low level of distortion and a wide range of reproduced frequencies, so it is better to use it on full-range speakers. People who have assembled amplifiers using this chip praise it for its high sound quality. This is one of the few microcircuits that truly “sounds well.” The sound quality is in no way inferior to the currently popular TDA7293/94. However, if errors are made in the assembly, high-quality work is not guaranteed.

Brief description and advantages

This chip is a single-channel Hi-Fi amplifier of class AB, the power of which is 50W. The chip has built-in SOAR protection, thermal protection (overheating protection) and a "Mute" mode.

The advantages include the absence of clicks when turning on and off, the presence of protection, low harmonic and intermodulation distortion, low thermal resistance, and more. There is practically nothing to highlight among the shortcomings, except failure when the voltage “runs” (the power supply must be more or less stable) and the relatively high price

Briefly about appearance

The chip is available in a SIP package with 9 long legs. The pitch of the legs is 2.54mm. On the front side there are inscriptions and a logo, and on the back there is a heat sink - it is connected to the 4th leg, and the 4th leg is the “-” power supply. There are 2 eyelets on the sides for attaching the radiator.

The original or a fake?

Many people ask this question, I will try to answer you.

So. The microcircuit must be carefully made, the legs must be smooth, minor deformation is allowed, since it is unknown how they were handled in a warehouse or store

The inscription... It can be made either with white paint or with a regular laser, the two chips above are for comparison (both are original). If the inscription is painted, there should ALWAYS be a vertical stripe on the chip, separated by an eyelet. Don't be confused by the "TAIWAN" inscription - it's okay, the sound quality of such copies is no worse than those without this inscription. By the way, almost half of the radio components are made in Taiwan and neighboring countries. This inscription is not found on all microcircuits.

I also advise you to pay attention to the second line. If it contains only numbers (there should be 5 of them) - these are “old” production microcircuits. The inscription on them is wider, and the heat sink may also have a different shape. If the inscription on the microcircuit is applied with a laser and the second line contains only 5 digits, there should be a vertical stripe on the microcircuit

The logo on the microcircuit must be present and only “PHILIPS”! As far as I know, production ceased long before NXP was founded, and this is 2006. If you come across this microcircuit with the NXP logo, there is one of two things - they started producing the microcircuit again or it is a typical “leftist”

It is also necessary to have depressions in the shape of circles, as in the photo. If they are not there, it is a fake.

Perhaps there are still ways to identify the “leftist”, but you shouldn’t stress over this issue so much. There are only a few cases of marriage.

Technical characteristics of the microcircuit

* Input impedance and gain are adjusted by external elements

Below is a table of approximate output powers depending on power supply and load resistance

Supply voltage		Load resistance
		4 ohm	8 ohm
		10W	6W
+-16.5V		28W	12W
		48W	28W
		58W	32W
		69W	40W

Schematic diagram

The diagram is taken from the datasheet (May 1992)

It's too bulky... I had to redraw it:

The circuit differs slightly from that provided by the manufacturer, all the characteristics given above are exactly for THIS circuit. There are several differences and they are all aimed at improving the sound - first of all, filter capacitors were installed, the “voltage boost” was removed (more on that a little later) and the value of resistor R6 was changed.

Now in more detail about each component. C1 is the input coupling capacitor. It passes through only the alternating voltage signal. It also affects the frequency response - the smaller the capacitance, the smaller the bass and, accordingly, the larger the capacitance, the greater the bass. I would not recommend setting it to more than 4.7 µF, since the manufacturer has provided for everything - with the capacitance of this capacitor equal to 1 µF, the amplifier reproduces the declared frequencies. Use a film capacitor, in extreme cases an electrolytic one (non-polar is desirable), but not a ceramic one! R1 reduces the input resistance, and together with C2 forms a filter against input noise.

As with any operational amplifier, the gain can be set here. This is done using R2 and R7. At these ratings, the gain is 30 dB (may deviate slightly). C4 affects the activation of SOAR and Mute protection, R5 affects the smooth charging and discharging of the capacitor, and therefore there are no clicks when the amplifier is turned on and off. C5 and R6 form the so-called Zobel chain. Its task is to prevent the amplifier from self-excitation, as well as to stabilize the frequency response. C6-C10 suppress power supply ripples and protect against voltage sags.
The resistors in this circuit can be taken with any power, for example I use the standard 0.25W. Capacitors for a voltage of at least 35V, except for C10 - I use 100V in my circuit, although 63V should be enough. All components must be checked for serviceability before soldering!

Amplifier circuit with "voltage boost"

This version of the circuit is taken from the datasheet. It differs from the above-described scheme in the presence of elements C3, R3 and R4.
This option will allow you to get up to 4W more than stated (at ±23V). But with this inclusion, distortion may increase slightly. Resistors R3 and R4 should be used at 0.25W. I couldn’t handle it at 0.125W. Capacitor C3 - 35V and above.

This circuit requires the use of two microcircuits. One gives a positive signal at the output, the other a negative one. With this connection, you can remove more than 100W into 8 ohms.

According to those who gathered, this scheme is absolutely workable and I even have a more detailed table of approximate output powers. It's below:

And if you experiment, for example, at ±23V you connect a 4 ohm load, you can get up to 200W! Provided that the radiators do not heat up too much, the 150W microcircuit will be easily pulled into the bridge.

This design is good to use in subwoofers.

Operation with external output transistors

The microcircuit is essentially a powerful operational amplifier and it can be further boosted by adding a pair of complementary transistors to the output. This option has not yet been tested, but it is theoretically possible. You can also power up the bridge circuit of the amplifier by attaching a pair of complementary transistors to the output of each microcircuit

Operation with unipolar power supply

At the very beginning of the datasheet, I found lines that say that the microcircuit also works with single-supply power. Where is the diagram then? Alas, it’s not in the datasheet, I couldn’t find it on the Internet... I don’t know, maybe such a circuit exists somewhere, but I haven’t seen one... The only thing I can recommend is TDA1512 or TDA1520. The sound is excellent, but they are powered from a single-polar supply, and the output capacitor can slightly spoil the picture. Finding them is quite problematic; they were produced a very long time ago and were discontinued a long time ago. The inscriptions on them can be of various shapes; there is no need to check them for “fake” - there have been no cases of refusal.

Both microcircuits are Hi-Fi class AB amplifiers. Power is about 20W at +33V into a 4 ohm load. I won’t give the diagrams (the topic is still about the TDA1514A). You can download printed circuit boards for them at the end of the article.

Nutrition

For stable operation of the microcircuit, you need a power source with a voltage from ±8 to ±30V with a current of at least 1.5A. Power must be supplied with thick wires, the input wires should be kept as far away from the output wires and the power source as possible
You can power it with an ordinary simple power supply, which includes a mains transformer, a diode bridge, filter tanks and, if desired, chokes. To obtain ±24V, you need a transformer with two 18V secondary windings with a current of more than 1.5A for one microcircuit.

You can use switching power supplies, for example the simplest one, on IR2153. Here is his diagram:

This UPS is made using a half-bridge circuit, frequency 47 kHz (set using R4 and C4). Diodes VD3-VD6 ultrafast or Schottky

It is possible to use this amplifier in a car using a boost converter. On the same IR2153, here is the diagram:

The converter is made according to the Push-Pull scheme. Frequency 47kHz. Rectifier diodes need ultrafast or Schottky ones. Transformer calculations can also be performed in ExcellentIT. The chokes in both schemes will be “recommended” by ExcellentIT itself. You need to count them in the Drossel program. The author of the program is the same -

I would like to say a few words about the IR2153 - the power supplies and converters are quite good, but the microcircuit does not provide stabilization of the output voltage and therefore it will change depending on the supply voltage, and it will also sag.

It is not necessary to use IR2153 or switching power supplies in general. You can do it simpler - like in the old days, a regular transformer with a diode bridge and huge power supply capacities. This is what its diagram looks like:

C1 and C4 at least 4700 µF, for a voltage of at least 35V. C2 and C3 - ceramics or film.

Printed circuit boards

Now I have the following collection of boards:
a) the main one - it can be seen in the photo below.
b) slightly modified first (main). All tracks have been increased in width, the power ones are much wider, the elements have been slightly moved.
c) bridge circuit. The board is not drawn very well, but it is functional
d) the first version of the PP is the first trial version, there is not enough Zobel chain, but I assembled it this way and it works. There is even a photo (below)
d) printed circuit board fromXandR_man - found it on the forum of the Soldering Iron site. What can I say... Strictly a diagram from the datasheet. Moreover, I saw with my own eyes sets based on this signet!
In addition, you can draw the board yourself if you are not satisfied with the ones provided.

Soldering

After you have made the board and checked all the parts for serviceability, you can start soldering.
Tin the entire board, and tin the power traces with as thick a layer of solder as possible
All jumpers are soldered in first (their thickness should be as large as possible in the power sections), and then all components increase in size. The microcircuit is soldered last. I advise you not to cut the legs, but solder them as they are. You can then bend it to make it easier to fit on the radiator.

The microcircuit is protected from static electricity, so you can solder with the soldering iron turned on, even while sitting in woolen clothes.

However, it is necessary to solder so that the chip does not overheat. For reliability, you can attach it to the radiator by one eye during soldering. You can do it in two, there won’t be any difference, as long as the crystal inside doesn’t overheat.

Setup and first launch

After all the elements and wires are soldered, a “test run” is necessary. Screw the microcircuit onto the radiator and connect the input wire to ground. You can connect future speakers as a load, but in general, to prevent them from “flying out” in a split second due to defects or installation errors, use a powerful resistor as a load. If it crashes, you know that you made a mistake, or you got a defect (the microcircuit is meant). Fortunately, such cases almost never happen, unlike TDA7293 and others, of which you can get a bunch of them from one batch in a store and, as it turns out later, they are all defective.

However, I want to make a small note. Keep your wires as short as possible. It happened that I just lengthened the output wires and began to hear a hum in the speakers, similar to “constant”. Moreover, when the amplifier was turned on, due to the “constant” mode, the speaker produced a hum that disappeared after 1-2 seconds. Now I have wires coming out of the board, a maximum of 25 cm and going straight to the speaker - the amplifier turns on silently and works without problems! Also pay attention to the input wires - use a shielded wire; it shouldn’t be long either. Follow simple requirements and you will succeed!

If nothing happened to the resistor, turn off the power, attach the input wires to the signal source, connect your speakers and apply power. You can hear a slight hum in the speakers - this indicates that the amplifier is working! Give a signal and enjoy the sound (if everything is perfectly assembled). If it “grunts” or “farts” - look at the food, at the correctness of assembly, because, as has been discovered in practice, there are no such “nasty” specimens that, with proper assembly and excellent nutrition, worked crookedly...

What the finished amplifier looks like

Here is a series of photographs taken in December 2012. The boards are just after soldering. Then I assembled it to make sure the microcircuits were working.

But my first amplifier, only the board has survived to this day, all the parts went to other circuits, and the microcircuit itself failed due to alternating voltage coming into contact with it

Below are the latest photos:

Unfortunately, my UPS is at the manufacturing stage, and I previously powered the microcircuit from two identical batteries and a small transformer with a diode bridge and small power supply capacities, in the end it was±25V. Two such microcircuits with four speakers from the Sharp music center played so well that even the objects on the tables “danced to the music,” the windows rang, and the body felt the power quite well. I can’t remove this now, but there is a ±16V power supply, from it you can get up to 20W at 4 ohms... Here is a video for you as proof that the amplifier is absolutely working!

Acknowledgments

I express my deep gratitude to the users of the “Soldering Iron” site forum, and specifically, a huge thank you to the user for some help, and I also thank many others (sorry for not calling you by nickname) for their honest feedback, which pushed me to build this amplifier. Without all of you, this article might not have been written.

Completion

The microcircuit has a number of advantages, first of all, excellent sound. Many microcircuits of this class may even be inferior in sound quality, but this depends on the quality of the assembly. Bad assembly - bad sound. Take electronic circuit assembly seriously. I strongly do not recommend soldering this amplifier by surface mounting - this can only worsen the sound, or lead to self-excitation, and subsequently complete failure.

I collected almost all the information that I checked myself and could ask other people who assembled this amplifier. It's a pity that I don't have an oscilloscope - without it, my statements about sound quality mean nothing... But I will continue to say that it sounds just great! Those who collected this amplifier will understand me!

If you have any questions, write to me on the forum of the Soldering Iron site. to discuss amplifiers on this chip, you can ask there.

I hope the article was useful to you. Good luck to you! Regards, Yuri.

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
	Chip	TDA1514A	1			To notepad
C1	Capacitor	1 µF	1			To notepad
C2	Capacitor	220 pF	1			To notepad
C4		3.3uF	1			To notepad
C5	Capacitor	22 nF	1			To notepad
C6, C8	Electrolytic capacitor	1000uF	2			To notepad
S7, S9	Capacitor	470 nF	2			To notepad
C10	Electrolytic capacitor	100uF	1	100V		To notepad
R1	Resistor	20 kOhm	1			To notepad
R2	Resistor	680 Ohm	1			To notepad
R5	Resistor	470 kOhm	1			To notepad
R6	Resistor	10 ohm	1	Selected during setup		To notepad
R7	Resistor	22 kOhm	1			To notepad
	Circuit with voltage boost
	Chip	TDA1514A	1			To notepad
C1	Capacitor	1 µF	1			To notepad
C2	Capacitor	220 pF	1			To notepad
C3	Electrolytic capacitor	220uF	1	From 35V and above		To notepad
C4	Electrolytic capacitor	3.3uF	1			To notepad
C5	Capacitor	22 nF	1			To notepad
C6, C8	Electrolytic capacitor	1000uF	2			To notepad
S7, S9	Capacitor	470 nF	2			To notepad
C10	Electrolytic capacitor	100uF	1	100V		To notepad
R1	Resistor	20 kOhm	1			To notepad
R2	Resistor	680 Ohm	1			To notepad
R3	Resistor	47 Ohm	1	Selected during setup		To notepad
R4	Resistor	82 Ohm	1	Selected during setup		To notepad
R5	Resistor	470 kOhm	1			To notepad
R6	Resistor	10 ohm	1	Selected during setup		To notepad
R7	Resistor	22 kOhm	1			To notepad
	Bridge connection
	Chip	TDA1514A	2			To notepad
C1	Capacitor	1 µF	1			To notepad
C2	Capacitor	220 pF	1			To notepad
C4	Electrolytic capacitor	3.3uF	1			To notepad
C5, C14, C16	Capacitor	22 nF	3			To notepad
C6, C8	Electrolytic capacitor	1000uF	2			To notepad
S7, S9	Capacitor	470 nF	2			To notepad
C13, C15	Electrolytic capacitor	3.3uF	2			To notepad
R1, R7	Resistor	20 kOhm	2			To notepad
R2, R8	Resistor	680 Ohm	2			To notepad
R5, R9	Resistor	470 kOhm	2			To notepad
R6, R10	Resistor	10 ohm	2	Selected during setup		To notepad
R11	Resistor	1.3 kOhm	1			To notepad
R12, R13	Resistor	22 kOhm	2			To notepad
	Impulse power block
IC1	Power Driver and MOSFET	IR2153	1			To notepad
VT1, VT2	MOSFET transistor	IRF740	2			To notepad
VD1, VD2	Rectifier diode	SF18	2			To notepad
VD3-VD6	Diode	Any Schottky	4	Ultrafast diodes or Schottky		To notepad
VDS1	Diode bridge		1	Diode bridge for the required current		To notepad
C1, C2	Electrolytic capacitor	680uF	2	200V		To notepad
C3	Capacitor	10 nF	1	400V		To notepad
C4	Capacitor	1000 pF	1			To notepad
C5	Electrolytic capacitor	100uF	1			To notepad
C6	Capacitor	470 nF	1			To notepad
C7	Capacitor	1 nF	1

Supplementing the TDA7294 microcircuit with powerful complementary transistors controlled from its output stage increases the rated output power of the UMZCH to 100 W with a 4 Ohm load. In addition to domestic transistors, more powerful imported ones can be recommended for this purpose. The author's use of a low-noise fan - a "cooler" from a computer processor - in the design made it possible to reduce the size of the heat sinks and amplifier.

The UMZCH on the TDA7294 chip has gained well-deserved popularity among radio amateurs. At a minimum cost, you can assemble a high-quality UMZCH.

The amplifier version based on the TDA7294 chip turns out to be more reliable when operating with a real load, but its main technical characteristics remain the same: the low nonlinear distortion coefficient for an output power of 5 W increases to 0.5% at a power of more than 50 W. It is not possible to achieve an output power of more than 80 W with a 4 ohm load. The bridge circuit for connecting the microcircuit, recommended by the manufacturer, does not provide for the ability to work with a load with a resistance of 4 ohms.

The version of the amplifier shown here, its circuit shown in Fig. 1, solves the problem of increasing the output power and reducing the coefficient of nonlinear distortion with an output power of more than 50 W compared to a typical microcircuit circuit. To reduce the load on the output stage of the microcircuit, an additional push-pull repeater is built in on powerful bipolar transistors that operate in mode B. There are no “ladder” distortions in the output stage because the output of the microcircuit is also connected to the load through a low-resistance resistor, and the OOS voltage is removed from emitter circuit of additional transistors. Resistor R7 ensures rapid discharge of the capacitance of the emitter junctions of the output stage transistors.

Main technical characteristics:

Input impedance: 22 kOhm

Input voltage: 0.8V

Rated output power: 100W/4ohm

Reproducible frequency band: 20 – 20000 Hz

The disadvantage of the proposed UMZCH, in comparison with the version using a standard microcircuit connection circuit, is a steeper increase in nonlinear distortions at an output power close to the maximum. In a typical circuit, the output signal limitation has a “softer” character.

Simplified block diagram of TDA7294 shown in Fig. 1 allows us to make the following assumption. Resistive current sensors are included in the circuits of the output transistors of the microcircuit, therefore, when the output signal voltage is close to the supply voltage (when the current through the powerful transistors of the microcircuit is maximum), the protection unit begins to smoothly limit the current in the load; field-effect transistors of the output stage probably also contribute to a softer limitation. The additional transistors of this UMZCH are not covered by such a tracking circuit, and a “hard” limitation of the output signal occurs, which is noticeable by ear.

A decrease in capacitance C6, C7 in comparison with that indicated in the diagram leads to unstable operation of the UMZCH at high power, but an increase in capacitance can lead to failure of transistors VT1, VT2, since when shorted in the load, the microcircuit protection unit does not always provide reliable protection for additional transistors until the fuses FU1, FU2 trip. The amplifier is powered by an unstabilized power supply from a 220 V network.

Not all parts purchased on radio markets are of high quality. There are microcircuits that are prone to self-excitation. In the described embodiment, self-excitation of some microcircuits must be eliminated by selecting capacitor C6.

In the UMZCH according to the scheme proposed here, even with slight self-excitation, “step” type distortions occur. If it is not possible to replace the “unsuccessful” microcircuit, the effect can be eliminated by soldering a capacitor with a capacity of 0.047-0.15 μF in parallel with resistor R7. Self-excitation is also eliminated by reducing the depth of feedback (increasing the resistance of resistor R3), while increasing the sensitivity of the amplifier.

Parts used in the amplifier:

1. MLT resistors
2. capacitors C1 - K73-17, KM-6; S2 – KT-1, KM-5; C8 – K73-17; SZ-S7 - K50-35 or imported.
3. choke L1 - 25 turns of PEV-2 wire with a diameter of 1 mm - wound on a frame with a diameter of 5 mm in two layers.

Two amplifier channels are assembled on a printed circuit board made of one-sided foil fiberglass 2 mm thick; its drawing with the arrangement of elements is shown in Fig. 2 (the outline of the fans is conditionally transparent).

There is no space provided on the printed circuit board for blocking capacitors C9, C10. The use of transistors that differ significantly in the base current transfer coefficient has practically no effect on reliability and sound quality.

The absence of quiescent current allows you to use a fan (“cooler”) from a Pentium processor to cool the heat sinks of both channels of the amplifier. The board and fans must be installed so that the flow of warm air does not heat other parts of the amplifier.

Powerful transistors are mounted parallel to the plane of the printed circuit board with a metal surface of the heat sink to the cooler. On the flat side of the cooler, it is necessary to drill through holes with a diameter of 2.5 mm, coinciding with the holes in the printed circuit board, then cut the MZ thread. Through the holes in the board, the fan is pressed against the transistors with screws. Thin mica spacers must be placed on them and lubricated with heat-conducting paste.

Under the heads of the screws on the side of the tracks, you need to place washers with a diameter of 10-12 mm or a small metal plate in order to firmly press the transistors to the surface of the heat sink. Place thin cardboard 0.5-0.8 mm thick between the printed circuit board and the transistors; it will ensure uniform pressing of the transistors to the plane of the fan, since their thickness is not always the same, even for those manufactured in the same production batch.

The DA1 chip is located on an additional heat sink with an effective surface area of ​​at least 50 cm 2 .

It is advisable to “strengthen” the tracks on the printed circuit board through which the supply voltage is supplied to the output transistors by soldering tinned copper wire with a diameter of about 1 mm along them.

An amplifier assembled from serviceable parts does not require adjustment and can be repeated even by novice radio amateurs. Operation for two years showed its high reliability.

With new wiring, as well as with mounting the microcircuit and transistors on one radiator.