50 watt power MOSFET amplifier circuit diagram

This is a MOSFET transistor based power amplifier circuit that can be operated between +35V to -35V range. The input voltage is pre filtered and pre amplified before applying to the MOSFET switch. The pre audio amplifier is a differential amplifier section with PNP transistor.What is differential amplifier? A difference amplifier is a type of power amp with two differential inputs which amplify the difference between two input signals. Here we are dealing with the circuit diagram and working of high voltage differential amplifier using IRF9530 and IRF530 MOSFET. You need a dual power supply circuit for this amplifier which I had posted earlier.

Recommended: MOSFET Working Animation

Don’t forget to have a look at other amplifier circuits in the related posts section at the bottom.

Circuit diagram of MOSFET power amp

MOSFET amplifier circuit
Click on the circuit diagram for enlarged view

Components required

  1. Dual power supply
  2. Resistors ¼ watt (10Ω; 560Ω; 680Ω; 820Ω; 1.2kΩ; 2.2kΩ; 2.7Ωk x 2 4.7kΩ x 2; 10kΩ; 15kΩ; 47kΩ x 2)
  3. Preset (1kΩ)
  4. Electrolytic capacitors (47µF,16V x 2; 100µF,50V x 4)
  5. Capacitors (220pF; 68nF)
  6. Inductor (12 turns of enameled copper wire on a 1cm diameter plastic former- 0.1µH)
  7. Diode (1N4002)
  8. BJT transistors (BC556 x 2; BC546 x 2)
  9. MOSFET (IRF530; IRF 9530)
  10. Speaker (8Ω)

Working of 50 Watt amplifier

  • Input audio signal is pre filtered using a low pass filter and applied to the differential amplifier based on transistors Q5 and Q6.
  • C7 removes the high frequency noise signals and R16 limits the current through C7.
  • The intermediate stage consisting of Q3 and Q4 acts as a driver to the next MOSFET stage.
  • To adjust the quiescent current, a preset is connected at the base of Q3 transistor.
  • The IRF530 and IRF9530 MOSFETs are important part of this amplifier.
  • Here the two MOSFETs form a complementary push pull driver amplifier which is the output stage of our power amplifier.
  • R14 and C8 reduce the unwanted noise occurring in the MOSFET amplifier.
  • The capacitors C5 and C3 are power supply filters. The output speaker is driven via an inductor to make noise free amplifier.

Remember: Provide a suitable heat sink for MOSFETs.

Pinout of MOSFETs IRF530, IRF9530, BC556 & BC546

22 thoughts on “50 watt power MOSFET amplifier circuit diagram

  1. I have made this circuit… Everything is fine but only one problem occurs that when i turn on the supply there is very little sound even at max input of mobile…. But after it when i disconnect the speaker wire and again connect it then it produces good sound….. Can you please tell me what’s the problem?

    • Make sure the power supply is working properly. Make sure the capacitor in the power supply is not leaking or connected in reverse. I suggest using Electrolytic Capacitors with about 10,000 ( uF ) microFarads and the ( W V ) Working Volts in the 50 or higher range. If possible, use several 10,000 uF Electrolytic Capacitors in parallel to reduce ripple ( Distortion ).

  2. Sorry, its not about this circuit. I’m new in electronics and I’m in real problem here. I have a 400w sterio amplifier using IRNF150n. It was working fine. But I accidently touched a 220nf box capacitor using a tester (shorted). There was a spark but no burns. Still I replaced that capacitor. But now that side is not producing enough high and middle frequency. Sound level is low on that side. When I switch on that amp, the speaker pulls outward or downward after a second slowly, while the other speaker pulls instantly. Can you please suggest me how to solve it?. The amp was of my friend and he gave it to replace some pots and switches. He’s willing to pay for another board. (the board was an old one).But I feel guilty of ruining it. Please help me

  3. How did you compute with all that components? Well for example. Given 50W and RL of 8ohm? How to compute the components???

  4. Sir how i made a -30 0 +30 dual power supply..? You already mentioned another post, but there only +5 0 -5 only..?

  5. hi; I am from Venezuela and I Have been reading these articles so interesting.. I would like to build this amplifier because its output uses Mosfet transistors and I have never used such transistor but bipolars.. What changes must be made in order to increase the supply voltage, say +70 -70 Vdc?? to get more power with this amplifier, or do you recommend me other mosfet amplifier circuit?? thanks for your attention and response.

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