TDA7294 100W Audio Amplifier

100W Audio Amplifier TDA7294.

TDA7294 is an integrated, monolithic, Class AB audio amplifier designed specifically for Hi-Fi applications. The IC has a DMOS output stage and can deliver 100W RMS into an 8Ohm speaker at +/-38V dual supply. The TDA7294 has low noise, low distortion, good ripple rejection and can be operated from a wide range of supply voltages. The IC has built in short circuit protection and thermal shutdown circuitries. The IC is available in multiwatt 15V and multiwatt 15H packages.

Description.

In the circuit TDA7294 is configured to provide 100W output power into an 8Ohm loudspeaker at +/- 38V supply. C8 is the input coupling capacitor and the input is applied to the non-inverting input (Pin3) of the IC. C3 and C9 are power supply filter capacitors while C10 and C4 are bypass capacitors. C2 is the bootstrap capacitor. RC network comprising of R1 and C1 improves the high frequency stability of the amplifier and also prevents oscillations. R2 and C6 sets the mute time constant while R3 and C5 sets the standby time constant. S1 and the mute switch and S2 are the standby switch. R5 is the input resistance and the amplifiers input impedance has a direct relationship to its value. R4 and R6 is used for setting type closed loop gain and with the used value, gain is 30dB. C2 is a feedback capacitor and it also provides DC decoupling.

Circuit Diagram.

100W amplifier TDA7294

TDA7294 100W amplifier

Notes.

  • The supply voltage range is +/- 10V to =/-40V DC.
  • Heat sink is required and its thermal resistance should be around 0.038 degree Celsius/Watt.
  • Use an 8 Ohm 150W speaker as the load.
  • For 100W output the supply voltage must be +/-38VDC.
  • The power supply must be well filtered and free of ripples.
  • If ripples are present in the power supply it may cause oscillations.
  • VM = 1.5V is the mute ON threshold and VM=3.5V is the mute OFF threshold.
  • VSTBY = 1.5V is the standby on threshold and VSTBY = 3.5V is the standby OFF threshold.
  • Typical input resistance of TDA7294 is 100KiloOhm.
  • Frequency response is 20Hz to 20KHz.
  • 145 degree Celsius is the threshold for thermal shutdown. Slew rate of TDA7294 is 10V/microsecond and the open loop voltage gain is 80 dB.
  • Quiescent current of TDA7294 is approximately 30mA and its maximum value is 65mA.
Show Comments

75 thoughts on “TDA7294 100W Audio Amplifier

  1. mess

    hi, anybody have pcb layout for this…and where do I get power for VM and VSTBY…or can I just leave it without connecting them….thanks

    Reply
  2. gayan

    i read the notes for this circuits. but i cant understand what is VM and VSTBY . how can i connect them to the circuit please help me

    Reply
  3. yesh

    Hello sir ,please I need a diagram that will help me amplify my factory set car audio from 50watts too 150 / 250 watts from a 12vdc supply with parts list please I will be highly appreciated

    Reply
    • Seetharaman

      Hi Yesh It is not directly possible without driver and output transformers with 12 volt DC supply (like output stage in a PA Amplifier). With only a driver transformer and two darlinton power transistors or Mosfet transistors and a switched mode power supply of 12 VDC to plus minus 45 volts DC @ 5amps you can achieve 200 to 250 watts.

      Reply
  4. Midhunmp

    Sir, I am a +2student. I have 25 0 25 volt 5amp ac transformer . If i connect these to the circut what power will get on 4ohm load? Please help me sir….. I hope ur replay

    Reply
    • Seetharaman

      You will get 70 watts RMS into 4 ohms load at 0.5% and 85 Watts RMS into 4 ohms load at 10% distortion.

      Reply
  5. Midhunmp

    Sir
    I have 25v 5amp Ac transformer and 10inch 4ohm subwofr with bass filter. If i connect these to the circut what power will get. Please help me…

    Reply
  6. Goetz

    Hi folks, I’ve spent some time -nights- with 7294, asking it for 100 watts. It totally refused to do so.
    +/- 24 V at the rails you get 25 W over 4 Ohms – and that’s it. Higher voltage, more load (<4 Ohms) – you always get 25 Watts. This IC blushes in stage fright.
    But I was successful: ST itself offers a much more sophisticated circuitry in their datasheet and i managed to build it and to make it yell 110 Watts over 4 Ohms.
    But do I really need this kind of minstrel show:
    +/-25 V AND! +/-50 Volts, added eight transistors and so on? Everything well painted on a double layer pcb postcard?
    I don't need that staying with my old 2n6609 and 2n3773.
    Have Fun!
    Goetz from Germany

    Reply
    • Seetharaman

      Gnd indicates a common 0 volt line to power supply and the power supply zero volt, in turn to be connected to chassis at the input socket of the amplifier only (Please note only one point earthing is alone allowed to avoid hum loop etc).

      Reply
  7. Rex

    Seetharaman, i need a tone control circuit for this 100W amplifeir, but the tone control circuit i saw in this site uses +15V -15V power supply. But the 100w amplifeir needs +38V -38V Power supply.. My question is, if I CONNECT THE TONE CONTROL TO THE AMPLIFIER, will the -38V +38V POWER SUPPLY BE TOO MUCH FOR THE TONE CONTROL?

    Reply
  8. Rex

    Seetharaman, you said the power supply for this Amplifeir is +38V / -38V to get 100W output,… my Question is how many Ampere of current is needed, i mean, what is the Current Rating of the Transformer and the doide

    Reply
    • Seetharaman

      Hi Rex the transformer should be 27-0-27 with 150VA rating. Each winding should be capable of 2.5Amp to take care of surge requirement. You can use 3 amp rectifier itself. But I prefer you to use 6A10 6 amp rectifier capable of 400PIV.

      Reply
  9. bhaskar

    sir, I tried both u r 100w circuits (sub woofer also). I would like to install this in my car. 12v to 36v converter smps is pricing too much. pls post a affordable circuit if possible.

    Reply
  10. ACE

    Hi, ive patched up my circuit but it doesnt work at all, i followed the circuit diagram with all the right components. All the signals at the individual pins are correct, just that there isnt any output signal at pin 14. Couldn’t understand what could be the problem. i connect pin 9 and 10 to 3.5v individually.

    Please do get back to me. Using it for a project.
    Appreciate it alot!
    Thanks!!

    Reply
  11. Rex

    Seetharaman, thank you for the link you gave to me, for the brigde of this amplifeir, i visited the site but, the bridge amp circuit does not have good explanation and description, and the circuit diagram is not clear enough.. Circuitstoday.com is my best site, i dont like going to other site, please post the bridge amplifeir circuit here

    Reply
  12. Seetharaman

    Hj Ace 8 ohms 100 watts is sufficient. Still we recommend higher wattage since sudden peak power after a small pass can damage the speaker. If volume level is kept low and operate you can use even lower power speakers, but ensure that you operate at lower volume levels. use a suitable speaker protection like fast acting fuse etc.

    Reply
    • ace

      Hi,if i were to patch up my circuit onto a breadboard first, isit a must to install heatsink onto it too??

      do you have the PCB schematic layout for this circuit?appreciate it alot.

      Thank you!

      Reply
  13. Rex

    Seetharaman please wire this amp circuit to work with single power supply, please give us the circuit

    Reply
  14. Rex

    Seetharaman, is it possible to wire this 100W AMPLIFEIR CIRCUIT to work with a ‘single POWER supply? If yes, please give us the circuit diagram because i dont have center tapped transformer

    Reply
  15. Rex

    Please give the BRIDGE AMPLIFEIR Circuit using two of this IC’s TDA7294 as bridge amplifeir circuit with one output

    Reply
  16. rujtam

    hi sir,can I conect vm/vstby to +25V ct,,coz on my transform 20V not available,,18 and 25…
    So,what I must to do….

    Reply
    • Seetharaman

      Hi rujtam as per manifacturers datasheet, you may connect it to -Vs or ground hence voltage is not the criteria, it is only what ever you are supplying to the IC as Vs

      Reply
  17. yugandaraj

    HI sir. the supply given is +/- 38 v ,5A, but
    Can i use this circuit at 12V , 12 A ?? does it work ??

    Reply
  18. Seetharaman

    Hi Mansoor Pin No 9 and 10 should be connected to +20volt for playing and zero for muting or to keep the amplifier on standby.

    Reply
  19. seetharaman

    Hi Ramdas the recommended operating point of the amplifier is with plus minus 35 volts DC the power delivered will be 70 Watts RMS into 8 Ohms load with a distortion of 0.5% for plus minus 35 volts DC you have use a transformer with a rating of 25-0-25 volts @ 3 to 4 amps per channel.

    Reply
  20. Ramdas

    Dear Sir….

    How much ampere required for driving one channel of TDA7294
    Pls specify the Transformer details and Power supply details

    pls reply to my mail

    Reply
  21. seetharaman

    Hi Alex the absolute maximum voltage allowed is + & – 40volts with 30 volts transformer you will get 42 volts. The recommended voltage for 8 ohms speaker safe operation is 25 – 0 – 25volt 3 to 4 amps transformer.

    Reply
  22. seetharaman

    Hi You can build this logic, in sequence, in discrete digital ICs and connect the output through proper interface (drivers) to the individual equipment.

    Reply
    • Santhosh

      Hi Seetharaman,

      I tried building this amp and was successful. only when I try to install volume pot, since the first pin of the pot is connected to the chasis ground. I get a ground loop hum. If I connect the source directly to the amp there is no hum.

      Please suggest on how to connect a volume pot.

      Reply
  23. BENN

    Hello Sir,
    How do I design a circuit that works when the main power fails On-line UPS starts, after battery gets low then the generator starts automatically untill the battery gets charged. when battery is fully charged the generator stops and power comes from the UPS till the battery goes low, when main supply comes if generator is running it should stop and UPS should charge from the main power supply. is it possible?

    Reply

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