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  • This simple mosfet power audio amplifier circuit, with TL071C and 2 MOSFETs (IRF9530 and IRF530) can deliver up to 45W on 8Ω speaker or 70W on 4Ω speaker. This schematic is based on Siliconix application and on variations of voltage on the 2 resistors that are serial inserted on the voltage supplier of the operational amplifier driver. The MosFet transistor must be mounted on a heatsink with at least 1K/W.

    Schematic of the 70 Watts Mosfet Amplifier Circuit

    70 watt mosfet audio amplifier schematic

    The efficiency of this amplifier is 70%, distortions at cut frequency were at most 0.2% at 20Hz on 8Ω and 10W. With a power supply of ± 30V the mosfet audio amplifier can deliver 45W on 8 Ω and 70w on 4Ω. Remember that this audio amplifier is not protected on short-circuits so everytime you switch on check to see if the speaker is connected.

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    7 Responses to "70 Watt MOSFET Audio Amplifier"

    1. want to get product updates on my mail if possible

    2. love this site and yawn for more

    3. baretter says: on August 6, 2013 at 5:05 pm

      only for subwoofer. Too many intermodulation in high frequency

    4. NUSSLER NUSSLER says: on April 24, 2014 at 3:03 am

      Works just fine!
      No need to modify.

    5. Am testat schema pe simulator, nu merge de nici un fel. Nu scoate decat tensiune continua la iesirea operationalului. De fapt nu vad cum se pot deschide MOSFET-urile cand tensiunea Vgs trebuie sa fie mai mare de 5V. Nu vad cum isi creeaza alternantele luand practic un curent static din acele regulatoare de 15V. Oricum nu sunt adeptul unor astfel de amplificatoare. Am proiectat dupa literatura de specialitate folosind bipolare, avand performante foarte bune, distorsiuni de sub 0.01%, dar care sunt stabile si nu necesita reglaje de mare precizie.

    6. Sheikh Hassam says: on October 3, 2015 at 9:53 am

      What happens if speaker is not connected to it ?
      Please reply i am going to wire it….

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