20W audio amplifier using TDA7240

admin August 12, 2010 18 Comments

The audio amplifier shown here is based on the TDA7240 IC from ST Microelectronics. The TDA 7240 is an integrated audio amplifier IC that can deliver 20 watts of audio output power into a 4ohm load. The IC has minimum external parts count and is available in the 7 pin compact Heptawatt package. The IC also has a lot of good features like loud speaker protection, short circuit protection, low noise, low distortion etc. The circuit can be operated from a 12V DC single power supply and this makes it very useful in car audio applications.

Circuit diagram.


  • Assemble the circuit on a good quality PCB.
  • Use 12V DC for powering the circuit.
  • K1 can be a 4 ohm, 20W speaker.
  • S1 is the standby switch and S2 is the ON/OFF switch.
  • LED D2 is a power ON indicator.
  • Fit the IC to a proper heatsink.
  • December 5, 2017

    What if I use an 8 ohm speaker? Will the sound be half as powerful? Can I change the resisters R1 & R2 so that they limit less current. Say make then 1.1K?

  • aparecido furlaneto
    November 27, 2014

    qual os numeros dos pinos do tda 7240

  • December 23, 2013

    What is a standby suiitch? which is it use?

  • gerald
    September 7, 2013

    sir what must be the voltage of every capacitor.?

    • January 15, 2014

      C5 ,C6, and C7 should be at least 25v capacitor. The voltage of the capacitors that are directly attached to the power supply terminal should have the voltage greater than the voltage of power supply. For other capacitor you can use any type of voltage. But select at least 16v that’s what i recommend.

  • kamal
    January 11, 2011

    can we use 9V battery for supplying power to this circuit.plese respond quikly.

  • kamal
    January 11, 2011

    what is the use of standby switch S1

  • NOOB
    December 11, 2010

    yes to two separate speakers

  • Seetharaman
    December 1, 2010

    to two seperate speakers

  • noob
    December 1, 2010

    but if i make 2 of this amps two separate amps, how to Connect the wires from the two amplifiers.

  • Seetharaman
    December 1, 2010

    Hi Noob it is the best amplifier by ST. it is already a bridged amplifier. hence it is not possible to get 44 watts.http://www.datasheetcatalog.org/datasheets/105/378745_DS.pdf

  • noob
    December 1, 2010

    And how to bridge two of this amp to get one 44W amp

  • noob
    December 1, 2010

    Thank You for your reply.
    I’m planing to make a 5.1 Surround sound with 6 of this amplifiers, and now I’m curious about quality of this amplifier.

  • Seetharaman
    December 1, 2010

    hi noob you can use any number of amplifiers with single car battery.

  • noob
    November 30, 2010

    can i power two of this audio amps with one car battery, i want to make a Stereo amplifier but do not want to use 2 batteries, please answer.

    October 7, 2010

    Dear sir,
    I would like to get wor from computer power supply unit,witch can get 12v and 5v dc.As u know it is swtching power supply unit.Tell me what kind of changement it has to give to reach my goal.
    Please some one help me .Thank u

    Ki senevirathna

  • mohamed
    August 13, 2010

    pleaze,how can i make a traffic radar detection

  • Deepak
    August 12, 2010

    please give me the full details of “20W audio amplifier using TDA7420” ie. with their cost, the devices required…..

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