Mosfet Amplifier Circuits

This article lists various types of audio amplifier circuits using Mosfet.We have tested all these circuits in our lab and we found all of them performing satisfactorily.

Note: This article will be modified with new versions of Mosfet amplifier circuits in future;we shall notify new additions in our home page.

This article contains following list of amplifier circuits using Mosfet.

List of Circuits

1. 18 Watts Mosfet Amplifier

2. 10 Watt Mosfet Audio Amplifier

3. 50 Watt Mosfet Amplifier Circuit

1. 18 Watts Mosfet Audio Amplifier

Description

This circuit is an audio amplifier capable of delivering a decent output power with a minimum no: of parts , with considerable sound quality.
The amplifier employs only one transistor and two  MOSFETs  and few resistors and capacitors in a shunt feedback scheme.This tiny circuit can can deliver a whopping 18Watts into 8 Ohm speaker or 30W into a 4 Ohm speaker.

To get such a good performance and stability out of few components, a high quality well regulated DC power supply is necessary. This is very essential for reducing noise and getting a constant output power on varying loads. A good DC voltage regulator able of providing more than 2 Amps @ 40V can be used.You can expect such a power supply design very soon here in the power supply section.

Tips.

Assemble the board on a good quality PCB.Use a preamplifier board with tone control prior to this amplifier to get better performance. If you don’t want, then no problem because this amplifier circuit has enough punch with in it.

Components.

R1………………2K2 1/4W Resistance
R2………………27K 1/4W Resistance
R3,R4………….2K2 1/2W Trimmers
R5………………100R 1/4W Resistance
R6………………1K 1/4W Resistance
R7,R8……….. .330R 1/4W Resistance

C1 ………………22µF 25V Electrolytic Capacitance
C2 ………………47pF 63V Polyester or Ceramic Capacitance
C3,C4 …………100µF 50V Electrolytic Capacitance
C5 ………………2200µF 50V Electrolytic Capacitance

Q1 ………………BC550C
Q2 ………………IRF530 or MTP12N10
Q3……………… IRF9530 or MTP12P10

18 Watts Mosfet Amplifier Circuit Diagram.

18 watt mosfet amplifier circuit

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2. 10 Watts Mosfet Audio Amplifier

Description.

The diagram shown here is of a 10W MOSFET audio amplifier circuit that requires only a single supply. Single rail supply is seldom used in Class-B power amplifiers. Anyway, for low power applications like this it’s quite fine. Actually I got this circuit from an old cassette player that is still working and I am publishing it as it is. The powers MOSFETs BD512 and BD522 are obsolete now and so you may use any other matching power MOSFETS instead of them.
Transistors Q1 and Q2 is wired as a Darlington pair works as the preamplifier. Preset R3 controls the quiescent current while R2 provides feedback. Output is coupled to speaker through capacitor C4. Capacitor C5 is the power supply filter and C2 is the input DC decoupling capacitor.

Mosfet audio amplifier Circuit diagram

Mosfet amplifier circuit diagram and schematics
10 watts mosfet amplifier

Notes.

  • The circuit can be assembled on a vero board.
  • Use 30V DC for powering the circuit.
  • Do not expect much performance from this amplifier.
  • Capacitors C3, C4, C5 must be rated 50V and C2 can be 10V.
  • Use a 8 ohm 15W speaker as load.

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3. 50 Watts Mosfet Amplifier

Description:

The first stage of the amplifier is a differential amplifier based on transistors Q1 and Q2. Capacitor C8 is the input DC decoupler, R1 limits input current and capacitor C1 bypasses unwanted high frequencies. The second stage is the driver stage consisting of transistors Q3 and Q4. Output stage is a complementary push pull stage based on MOSFETs IRF530 and IRF9530.Output is coupled the speaker using the inductor L1. Network comprising of R15 and C5 is meant for noise reduction. Capacitors C6 and C7 are power supply filters. Preset R6 is meant for adjusting the quiescent current.

50 Watts Mosfet Amplifier Circuit diagram.

Mosfet amplifier circuit
Mosfet amplifier circuit – 50 watts

Notes:

  • Assemble the circuit on a good quality PCB.
  • Use +/-35V DC dual supply for powering the circuit.
  • For L1 make 12turns of enameled copper wire on a 1cm dia: plastic former.
  • C6 and C7 must be rated 50V; other electrolytic can be 10 or 15V.
  • Heat sink is necessary for the MOSFETs. A 8x4x4 inch finned Aluminum heat sink will do. There is no such thing as a heat sink that is too large.

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21 Responses to “Mosfet Amplifier Circuits”

  • d. oruson says:

    The 50-watt MOSFET amp circuit looks insteresting. It would be a lot more interesting if the input complementary pair were also FETs and the output was expanded to 2 or 3 pairs of MOSFETs to give 100 to 150 watts.
    How about it ?

  • amit says:

    I want a circuit of intex subwoofer model it10500suf plz give the circuit and oblige

  • Ramesh says:

    Sir please tell me the current amplifying transistors plzzzzzzz

    • Seetharaman says:

      Hi Ramesh any transistor is a current amplifier. If current gain of a transistor as per data sheet is say 100 at 1Amp. You require a base emitter current of 10 mA, to have the conduction of 1 amp through collector and emitter. The transistor cannot generate current it can only vary its collector emitter resistance to achieve the required current flow through collector emitter junction as per base emitter current bias.

  • JOHN says:

    Hi sir!! can i use IRF540,IRF9540 instead of IRF530,IRF9530? thank you!

  • Travis says:

    i’m a beginner but is vin the audio signal ? lets say from the 3.5mm jack

  • james says:

    let me know the swg of L1 IN 50W CIRCUIT

  • Claus_A says:

    About the 50W MOSFET Amp:
    I looked over and over again over the circuit but I cannot find C8. Is it missing or not needed for some reason (maybe the diff amp)?

  • ace says:

    hi, is anybody able to send me a 40W ciruit?

  • Messers! I have A 50 Watt 6 ohm subwoofer with 5 speakers 50 watt 5 ohm each. can you give me’n matching amplifier circuit diagram for my speaker set?

    • Seetharaman says:

      Hi Ali for your sub woofer speaker use motional feed back amplifier appeared in our column earlier. For the speakers use TDA2050 amplifiers each. you will enjoy its best quality sound with thumping bass and clear high notes

  • sadiq ali says:

    i have a lot of qunatity fet .iwant to use as transiter of fet . please if any one to know how use fet in the transister circuite rehmani sadiq lahore pakistan

  • Massimo Petrucci says:

    How about the quiescent current of 50w power amp?

    • Ollie Oz says:

      Power up the amplifier without applying an input signal.
      Let the circuit warm up for about 10 minutes.
      Measure the current in the positive supply.
      Adjust R6 until a current between 50 and 60mA is measured

  • paul says:

    i am requesting for an amplifier circuit diagram using transistors found in kenwood amplifier circuits

  • paul says:

    i want u to send me a circuit diagram of an amplifier that can drive 4 home speakers with its power circuit diagram

  • nithin says:

    plese give 2000watts rms power amplifier circute diagram

  • Thanasis says:

    Condidering the 50 Watts Amplifier:

    Can i use it with a microfone with the 2km FM transmitter(http://www.circuitstoday.com/2-km-fm-transmitter)?

  • Jonathan says:

    ON 18W Mosfet amplifier circuit
    R3 should be adjusted for 21 volts at the + side of C5, R4 should be slowly adjusted til there is 20 – 50 ma current flow into the drain of Q2 with no input signal. Use at least a 6 sq in heatsink on Q2/3. C5 needs be no more than 35 volts.