TDA7294 Based 170W High Power Audio Amplifier

TDA7294 Based 170W High Power Audio Amplifier

Components Required to Build TDA7294 Based Amplifier Circuit

This circuit is very easy to replicate because we used generic components to build it, you can find the pars requirements for this project in this section.

• TDA7294 IC - 2
• Screw Terminal 2.54 mm - 2
• Screw Terminal 5mm - 1
• 22k Ohms Resistor - 5
• 680 Ohm Resistor - 2
• 33k Ohm Resistor - 1
• 10k Ohm Resistor - 1
• 0.56uF Capacitor - 2
• 22µF Capacitor - 4
• Clad Board 50x 50mm - 1
• 6Amp Diode - 4
• 2200µF Capacitor - 2
• 0.22uF Capacitor - 2
• Heat Sink - 1

Choosing an Adequate Power Supply for the Project and Calculation

The TDA7294 IC can be powered from a dual or split power supply, in this way the performance and efficiency of the device increase greatly. That's why we'll be using a split power supply rather than a single one. The goal here is to find the right transformer, which can provide sufficient voltage and current to drive the amplifier properly.

Considering the 30-0-30 transformer shown above will output more or less 30-0-30V AC if the input supply voltage is 230V. But as AC mains input always drifts, the output will also drift. Considering that fact, we can now calculate the amplifier's supply voltage. The transformer gives us AC voltage and if we convert that into DC voltage, we will get

VsupplyDC = 30*(1.41) = 42.3VDC

This value is a little bit more than what we were targeting initially but it is within the absolute maximum rating of the device according to the datasheet. It can be clearly stated that the transformer can deliver 42.3VDC when the input is 230V AC. Now if we consider voltage drift of 5%, we can see that the maximum output voltage becomes

VmaxDC = (42.3 +2.4) = 44.77V

Which is well within the maximum supply voltage range of the TDA7294 IC

Thermal Requirements (Finding a Suitable Heat Sink)

Now that we have calculated the maximum power requirements, we can focus on finding a suitable heatsink for our amp circuit. For this build, I have chosen an aluminum, extrusion-type heat sink. Aluminum is a well-known substance for heat-sink because it's relatively inexpensive and exhibits good thermal performance. To verify the maximum junction temperature of the TDA7294 IC, we can use the popular thermal equations, which you can find in this Wikipedia link.

We use the general principle that the temperature drops ΔT across a given absolute thermal resistance RØ with a given heat flow Q through it. And the final formula would be,

​Qmax = (TJmax – (Tamb + ΔTHS)) / (R​ØJC + R​ØB + R​ØHA)

TJmax = 150 °C (typical for a silicon device)

Tamb = 29 °C (room temperature)

RØJC = 1.5 °C/W (for a typical TO-220 package)

RØB = 0.1 °C/W (typical value for an elastomer heat transfer pad for a TO-220 package)

RØHA = 2 °C/W

So, the final result becomes

Q = (150 - 29) / (1.5+0.1+2) = 15.14W

This means we have to dissipate 15.14 watts or more to prevent the device from overheating and getting damaged.

Note: Please note that at the time of making this project I didn't have any other big heat sink in my stockpile so I had to use the biggest one I have, for a smooth operation a bigger heat sink is recommended.

TDA7294 Based Amplifier Circuit Diagram

The circuit diagram for the TDA7294 amplifier circuit is given Above:

Components Required to Build TDA7294 Based Amplifier Circuit

This circuit is very easy to replicate because we used generic components to build it, you can find the pars requirements for this project in this section.

• TDA7294 IC - 2
• Screw Terminal 2.54 mm - 2
• Screw Terminal 5mm - 1
• 22k Ohms Resistor - 5
• 680 Ohm Resistor - 2
• 33k Ohm Resistor - 1
• 10k Ohm Resistor - 1
• 0.56uF Capacitor - 2
• 22µF Capacitor - 4
• Clad Board 50x 50mm - 1
• 6Amp Diode - 4
• 2200µF Capacitor - 2
• 0.22uF Capacitor - 2
• Heat Sink - 1

Detailed Explanation of TDA7294 Based Amplifier Circuit

Now as we have seen the complete schematic of the circuit, we can understand how the circuit works. We will start off with setting the gain of the amplifier as it’s the most important part.

Setting Gain for Amplifier

Setting up the gain for the amplifier is the most important step of the build, as a low gain setting may not provide enough power. And a high gain setting will certainly distort the amplified output signal of the circuit. With my experience, I can tell that setting the gain between 30 to 35 dB is good for playing audio with a smartphone or a USB audio kit. That is why we are going to focus on that.

In the above circuit, the output from pin 14 is fed back to pin 2 with a voltage divider configuration

Note: For setting up the amplifiers gain 1% or 0.5%, resistors must be used otherwise the stereo channels will produce different outputs.

Setting Input Filter for Amplifier 

The Resistor R1 in conjunction with C2 acts as a high pass filter that determines the lower end of the bandwidth. Other than that, the capacitor C2 acts as a DC blocking capacitor.

The cut-off frequency of the amplifier can be found by using the following formula shown below.

FC = 1 / (2πRC)

Where R and C are the values of the components.

To find the values of C, we have to rearrange the equation to:

C = 1 / (2π x 22000R x 3.5Hz) = 4.7uF

Note: It is recommended to use metal film oil capacitors for the best audio performance.

Setting Output and Configuring the Bootstrap

Next, we will set the output by configuring the bootstrap pin of the TDA7294 IC.

As you can clearly see that pin 6 of the IC is the bootstrap pin of the amplifier, which needs to be connected to the output pin (pin 14) of the IC and that's how this IC will get to know that it is configured in a bootstrap configuration.

Single Signal ST-BY/MUTE Control Circuit 

The above figure shows the possibility of using only one command for both st-by and mute functions. On both the pins, the maximum applicable range corresponds to the operating supply voltage which means by applying a range of input voltage this device can be put to standby or Mute mode.

Power Supply for Amplifier

A dual polarity power supply with proper decoupling capacitors is required to power the amplifier, and the schematic is shown below. Though the power supply section is not a part of the schematic, we are going to use this bridge rectifier configuration to power the circuit.

Circuit Construction

For the demonstration, the circuit is constructed on a handmade dotted perf board with the help of a schematic. Please note that if we are connecting a big load to the output of the amplifier, a huge amount of current will flow through, and to overcome that we have used a single strand of CAT6 cable to connect the power line in the perf board.

In order to make the circuit a little bit smaller and reduce complexity, I soldered some of the resistors to the backside of the perf board as shown in the below image.

Testing of TDA7294 Amplifier Circuit

The testing process will be very simple, we will connect the power supply and a load to the amplifier. Also, we will connect a temperature sensor to the amplifier to monitor the temperature and we will let it run.

To test the circuit, the following apparatus was used.

1. A transformer which has a 30-0-30 Tap
2. A 16Ω 180W speaker system as a load
3. Meco 108B+TRMS Multimeter as the temperature sensor
4. And my Samsung phone as an audio source

The Speaker System used is shown below. As mentioned earlier this is a 180 Watt speaker system with a 150 Watt RMS main speaker, a 15Watt tweeter for treble, and another 10 Watt of the speaker to output the vocal.

Also, you can see the room temperature was 22°C during the time of testing. At this moment, the amplifier was in an off state and the Multimeter was just showing the room temperature. Generally, the audio output of this amplifier is very good and can be improved by adding an Audio Tone Control Circuit alongside it.

You can see from the above image; the results were more or less great and the temperature of the IC didn't go beyond 41 °C during the testing. After using it for an hour the temperature did not move over 55°C.

This is how you can design a TDA7294-based High Power Audio Amplifier. If you have any questions, please leave them in the comment section below

Or You can Visit My Website Here