Friday, January 21, 2022

170W AB Class Bridge Mode Amplifier using TDA7294 IC + PCB

Fig. 1 - 170W AB Class Bridge Mode Amplifier using TDA7294 IC + PCB

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This is a Class AB Audio Power Amplifier, it uses two TDA7294 Integrated Circuits, in Bridge Mode to drive one or more power speakers.

The circuit provides a total output power of 170W, and this with good sound quality, powered from a symmetrical power supply.

The Amplifier responds very well to all audible frequency ranges, and has a minimalist, compact design, which makes this amplifier a good choice for an unprecedented range of application. 

IC Description

The TDA7294 is  a monolithic integrated circuit in Multiwatt15  package, intended  for  use  as  audio class   AB   amplifier   in   Hi-Fi   field   applications (Home Stereo, self powered loudspeakers, guitar amplifier, Top-class TV). 

Thanks to the wide voltage range and to the high out current capability it is able to supply the highest power into both 4Ω and 8Ω loads even in  presence of  poor supply regulation, with high Supply Voltage Rejection.

The  built  in  muting  function  with  turn  on  delay simplifies the remote operation avoiding switching on-off noises.

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The main Advantages offered by Bridge solution

  • High power performance with voltage level limiting supply.
  • Considerably high output power, even at high load values (i.e. 16 Ohm).
  • For a Speaker with 8Ω, Vs = ± 25V, the maximum output power obtained is 150 W, while with a Speaker with 16Ω, Vs = ± 35V, the maximum power is 170 W.


  • Operating Voltage Range (± 10V to ±40V)
  • DMOS Output Stage
  • High Output Power (Up to 100W musical)
  • Muting / Stand-By Functions
  • No Switch On/Off Noise
  • No Boucherot Cells
  • Very Low Distortion
  • Very Low noise 
  • Short-circuit protection
  • Thermal shutdown

Bridge Application

Our amplifier is configured in Bridge mode, where two TDA7294s ICs are used. With this type of configuration we get a pretty significant 170W of power, however there are two different configurations: 

For 8Ω Speaker - Vs = ± 25V, the maximum output power is 150 W.
For 16Ω Speaker - Vs = ± 35V, the maximum power is 170 W.

We know that the TDA7294, supports or speakers in mono version, however, for this application in Bridged configuration, the speaker impedance shouldn't be less than for reasons of dissipation and current carrying capacity of the Integrated Circuits.

The Schematic Circuit

In Figure 2 below we have the arrangement of the components of the amplifier circuit with the two TDA7294 ICs, and as we can see, the difficulty is not extreme.

Since there are few external components, making the amplifier circuit very simple to assemble, and a technician or hobbyist with average experience can assemble it without much difficulty. 

It is important to remember to be careful when assembling the circuit, not to invert any component such as capacitor diodes, or even when connecting the symmetrical voltage of the power supply.

Not to invert the voltage poles, because the integrated circuit or other components can be damaged.

Fig. 2 - Schematic 170W Amplifier Circuit in Bridge with Integrated Circuit TDA7294

Components List

  • Semiconductors
    • U1, U2 ........................ TDA7294 Integrated Circuit 
    • D1 ............................... 1N4148 Silicon Diode

  • Resistors
    • R1, R5, R6, R8, R10 ... 22K Resistor (red, red, orange, gold)
    • R2 ................................ 20K resistor (red, black, orange, gold)
    • R3 ................................ 10K resistor (brown, black, orange, gold)
    • R4 ................................ 30K resistor (orange, black, orange, gold)
    • R7, R9 ......................... 680Ω resistor (blue, gray, black, gold)

  • Capacitors
    • C1, C4 ......................... 1μF Ceramic/Polyester Capacitor
    • C2, C3, C5, C6 ............ 22μF Electrolytic Capacitor

  • Others
    • P1, P2 ......................... Screw Terminal Type 5mm 2-Pin Connector
    • P3 ................................ Screw Terminal Type 5mm 3-Pin Connector
    • J1 .................................Set of male connectors 3-Pin (Optional)
    • Other ........................... PCB, Wires, Speaker, etc.

Power Supply

The power supply will depend on which output power you will choose, which will also depend on how many Ohms your speaker will have. We have two versions:

Version 1 - 150W output.

  • Speaker must be 8Ω and the maximum voltage is for ±25V

Version 2 - 170W output.

  • Speaker must be 16Ω and the maximum voltage is ±35V.

Remember that for both versions a Symmetrical power supply is used, i.e. [ +VCC | GND | -VCC ]. With a current of at least 6 Amperes.

Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. - PCB 170W AB Class Bridge Mode Amplifier using TDA7294 IC

Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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My Best Regards!!!


  1. Hola, esta muy bueno, pero necesito el mismo mono bridge pero de alimentacion simple negativo y positivo

    1. ¡Hola! Juan carlos alberto!
      En el caso de un amplificador con dos TDA7294 en modo puente es casi imposible, ya que cada TDA está trabajando con medio ciclo, por lo que tenemos la tensión +Vdc, gnd, -Vdc.
      Tenemos un amplificador con el TDA7294 con fuente única, en este enlace:

      En modo puente, con un solo CI.


  2. Hi and good day
    It is my first time build on this amp and have encountered problems
    The PSU that i build is still symmetrical But i used two bridge rectifiers instead of one and with 4 10000uf 63V capasitors 2 on each side The transformer i am using is a RS Components Toroidal Part Number 671-9047.. All the caps onthe PCB is also 22uf 63 V
    The amps is working at low volume no problem ..But the moment i increase the volume and or the bass mid or treble the amp start to limit itself and the sound becomes distorted . The TDA7294 on the left gets extremley hot running at about 70 degrees C while the one on the right hand side at about 40 degrees C. The voltage seems to be stable running at about 35 VDC.Any suggestions to why this is happening. Any help would be highly appreceated ..Kind regards

    1. Hello @SCHALK
      You say you are using all 22uF pcb capacitors?
      Remember that capacitors C1 and C4 are 1uF, check this.
      Checks if the output voltage of the symmetric source are in the same proportion, with the amplifier on, see the working voltage, one being positive and the other negative.
      If everything is ok, check if the IC is original, it has already happened to us to buy the IC and it came damaged.
      My greetings!

    2. Yes C1 and C4 are indeed 1uf 100v polyester caps The supply was checked and symmetric +35 0 -35 VDC .The only difference on my supply is that i use 2 bridge rectifiers instead of the one and have put decoupling caps on all 4 points on the rectifiers 2 bleeder resistors 2.2K 5W on the caps I have bought 10 TDA7294 chips from Mantech Electronics in South Africa and 4 from RS Components What is strange however i bought a mono version kit from Jims Audio 2 seperate boards also bridgable and just build the mono version of the one side as a test and it does exactly the same ..Do you maybe have test voltages from different points on a working board that you can share with me ..I hope not that all the chips that i bought are dammaged .That would be a disaster...

    3. Just build the other channel using the same components ..Both amps connected to the same supply ..Tested transformer on a 10 Ohm load both positive and negitive supply lines give 3.5 amp no problem The other amp does exactly the same Using a 16 Ohm speaker The moment there is bass the circuit souds like it is limiting it self The left hand ic also gets extremley hot just like the other side Supply voltage stable at +34 0 -34 VDC

  3. What about PCB (or even circuit diagram) for TDA7375a in dual bridge mode? Is it available?