Thursday, December 22, 2011

Make a High Power 250 Watt MosFet Amplifier DJ Circuit

The powerful DJ 250 watt mosfet amplifier circuit design provided in this article is reasonably easy to build and will produce thumping music into the connected loudspeaker. Use of HEXFETs at the output ensures monstrous current and voltage amplification.

The involvement of MOSFETs or rather HEXFETs at the output stage of this 250 watt mosfet amplifier circuit promises high and efficient amplification of both voltage and current. The circuit particularly exhibits impressing features like low distortion and external offset voltage and quiescent current adjustments.

Input Stage

Output Stage

Circuit Description

This outstanding 250 watt mosfet amplifier circuit can be used as a DJ amplifier in concerts, parties, open grounds etc. The design being symmetrical produces negligible distortions. Let’s try to analyze the circuit details:
Referring to the circuit diagram, we see that the input stages primarily consists of two differential amplifiers. The blocks T1 and T2 are actually matched paired dual transistors in one package, but you may go for discrete transistors, just make sure their hFes are properly matched. Use a couple of BC 547 and BC 557 for the NPN and the PNP types respectively.
A differential configuration is probably the perfect way of integrating two signals, for example here the input and the feedback signals are mixed so efficiently.
Typically the ratio of the collector/emitter resistances of T1 determines the amplification of this stage.
The DC operating reference for T1 and T2 is received from a couple of transistors T3 and T4 along with the associated LEDs.
The above LED/ Transistor network also helps to provide a constant current source to the input stage as it virtually remains unaffected to ambient temperature variations, but preferably the LED/ transistor pair should be attached together by gluing them together or at least soldered very close to each other over the PCB.
Immediately after the coupling capacitor C1, the network comprising of R2, R3 and C2 forms an effective low pass filter and helps maintaining a bandwidth to a level suitable for the amplifier.
Another small network at the input, involving a 1M preset and a couple of 2M2 resistors helps adjusting the off-set voltage so that the DC component at the output of the amplifier stays at zero potential.
After the differential stage an intermediate driver stage is introduced comprising T5 and T7. The configuration consisting of T6, R9 and R17 forms a kind of variable voltage regulator, which is used to set the quiescent current consumption of the circuit.
The boosted signal from the above stage goes to the driver stage consisting of T8 and T9 which are effectively used to drive the output power stage involving the HEXFETs T10 and T11 where the signals ultimately undergoes a massive current and voltage amplification.
From the diagram it is clearly identifiable that T10 is a p-channel and T11 is an n-channel FET. This configuration allows efficient amplification of both current and voltage at this stage. The overall amplification is though limited to 3 due to the feedback wiring of R22/R23 and also with R8/C2. The limitation ensures low distortion at the output.
Unlike bipolar transistors, here the outputs stage incorporating HEXFETs have a distinct advantage over its age old counter part. HEXFETs being positive temperature coefficient devices are equipped with the inherent property of limiting their drain source as the case temperature tend to get too hot, safeguarding the device from thermal runaway situations and getting burnt off.
Resistor R26 and the series capacitor compensate the rising impedance of the loudspeaker at higher frequencies. Inductor L1 is placed to safeguard the loudspeaker from instantaneous rising peak signals.

Parts List

R1 = 100K
R2 = 100K
R3 = 2K
R4,5,6,7 = 33 E
R8 = 3K3,
R10,11,12,13 = 1K2,
R14,15 = 470E,
R16 = 3K3,
R17 = 470E,
R18,19,21,24 = 12E,
R22 = 220, 5 WATT
R20,25 = 220E,
R23 = 56E, 5 WATTS
R26 = 5E6, ½ WATT
C1 = 2.2uF, PPC,
C2 = 1n,
C3 = 330pF,
C6 = 0.1uF, mkt,
T3 = BC557B,
T4 = BC547B,
T7,9 = TIP32,
T5,6,8 = TIP31,
T10 = IRF9540,
T11 = IRF540,


  1. i will make it shortly .pls help me in making PCB . pls show the sony mega bass ckt diagram can i get genuine sony spare parts ?

    1. Procure a 10 by 10 inches copper clad first, then I'll tell you how to make a PCB

    2. already have copper clad and all the PCB making equipments and procedure problem is with design software which will be easier to me i don't know pls suggest . why sony music is too much clear than others ? i want the mega bass ckt diagram .

    3. I don't use a software, I do it on corelDraw....I will try to find a mega bass circuit, if I find one, I'll surely inform you.

    4. its too difficult, please please please make the PCB diagram for me please ..
      can you please design a 3D surround sound ckt for this amplifier .

    5. OK first try the following circuit:

  2. Hi swagatam,
    Thanks for your wonderful work here. It is not easy to update and maintain such a blog and i must commend you. I have a request for a 1,500watt amplifier. Please try to get me a working circuit diagram and detailed explanation for this. I will sincerely appreciate and reward you the little way i can.

    1. Hi Masterfiles, Please check out the following link, the design looks very promising and would possibly satisfy your needs:

    2. Thanks for the link sir.
      Could you please explain the circuit diagram? Also i doubt if i can find suitable transformer for the power supply section in my country. I have been searching with no result yet. can you suggest the way out?

    3. It's a standard design having a differential stage, followed by a driver stage and finally a power output stage.

      The transformer will need to be made-to-order, the high voltage is necessary for implementing the extreme high wattage output from the circuit, and for keeping the wires and the transformer dimensions smaller.

  3. Hi Swagatam,
    The coil just before the speaker has no value, what are your suggestions?


    1. it's 20 turns of 22swg enameled copper wire over a 1 ohm 5 watt resistor connected parallel to it.

  4. pls give a circuit for 5.2/7.2 surround system.

  5. what about the current & voltage & ohm's rate of this amp (what is the cost of IRF9540,IRF540

  6. if i will add 2 pair of more output mosfet then how much watt i will get

    1. You can do it, the power would increase substantially, just make sure to add a 0.22 ohm 1 watt resistors in series with the source of each mosfet, and also use separate gate resistors for each mosfets.

  7. plz sir, can u tell me the price of the two mosfet IRF9540,IRF540

  8. sir can u please tell me the cost of IRF9540,IRF540

    1. in my area(erode,tamilnadu,india) the IRF540 is 40/- rupees and IRF9540 is 50/- rupees only.

  9. I have two 6 ohm speakers and want to build a speaker system with very good quality right from scratch( from 3.5 mm jack). Got any circuit for that?

    1. you can try this one:

  10. I have 4 ohm super speakers.. will you help to make a amplifier at home for suitable for this 4 ohm speakers with simple way to understand circuits and gave a proper list to used equipments in this............... please help me...

    1. You can try the following circuit, this is much easier, but you will need a PCB for this:

  11. I really appreciate this circuits and others too. But I am sorry to say that it's of no use until you provide complete information like PCB design and complete parts list. Most of the projects I have seen here are just having few images, only few have parts list.

  12. Dear sir ,
    How to make offset zero. Wat is the supply voltage...
    Thanks n regards

    1. Dear style, you can do it by adjusting R9, supply is 30-0-30V DC 5 amps

  13. Dear Sir,
    the voltage and amps required for this ckt?

  14. Hi Sir, what happens to power sharing & output in an amplifier using transistors A1943 & C5200 because each is 100W power dissipation(power calculations of the output stage)?
    And what most contributes to how powerful an amplifier can be in TRANSISTOR AMPLIFIERS?

    1. Hi kakooza, the transistor number is not important, it's the specifications that matter, if the specs match then the transistor will work as efficiently as expected from them.

      the output devices primarily decide the power level of the amplifier, but only if the power supply is optimally rated, lower supply specs will result in poor output quality and distortions.

  15. Thanks so much for the detailed explanation. But one thing I would like to know before building it; have you or anyone else actually built the circuit using the given values?

    1. It has been tested by the "elektor electronics" engineers


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Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.
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