Motor Speed Control with MOSFET

There are many applications of MOSFET from the industrial sector to household appliances like motor speed control, light dimming, amplifying & switching electronic signals within electronic devices, as an inverter, high-frequency amplifier, and many more. Generally, these are available in different sizes to match various electronic projects necessities. MOSFETs are used whenever we need to control large voltages & currents with a small signal. This article provides brief information on one of the MOSFET applications like how to design a motor speed control with MOSFET.

Motor Speed Control with MOSFET

In modern society, the speed control of electric motors is everywhere because it is significant for different machines. The required function & the performance of electric motors are wide-ranging. When we focus on the motor’s speed control part, the speed control of stepper & servo motors can be done by a pulse train whereas the brushless DC & induction motor speed control can be done with DC voltage or an external resistor. At present in many industries, electrical motors are used as an indispensable power source. But, motor speed control is necessary because it directly affects the machine’s operation, quality & the result of the work.

The main intention of this is to design a circuit for controlling a DC motor speed with a MOSFET. A MOSFET is a type of transistor, used to amplify or switch voltages within circuits. The type of MOSFET used in this circuit is enhancement mode MOSFET which works only in the enhancement mode This means this transistor will be turned off whenever there is no voltage provided to the gate terminal & it will be turned ON whenever a voltage is provided. So makes the transistor ideal to use like a switch for controlling a DC motor.

DC motor is used in different applications like robots, appliances, toys, etc. So in many DC motor applications, motor speed & direction control is essential. Here we are going to explain how to design a simple DC motor controller with a MOSFET.

Required Components:

The required components to make this DC motor controller include a 12V battery, 100K potentiometer, IRF540N E-MOSFET, a DC motor, and a switch.


The connections of this DC motor speed control with IRF540N EMOSFET follow as;

DC Motor Speed Control with MOSFET
DC Motor Speed Control with MOSFET

The IRF540 E-MOSFET gate terminal is connected to the potentiometer, the source terminal is connected to the positive wire of the motor, and the drain terminal of the MOSFET is connected to the positive terminal of the battery through a switch.

The motor negative wire is connected to the negative terminal of the battery.

The potentiometer output terminal is connected to the gate terminal of MOSFET, GND is connected to the negative terminal of the battery through a negative wire of the motor, and the VCC pin is connected to the positive terminal of the battery through a drain terminal of MOSFET and switch.


Once the switch ‘S’ is closed the voltage supply at the MOSFET gate terminal causes the current supply from the drain (D) terminal to the source (S). After that current starts flowing throughout the DC motor & the motor begins to turn. The sum of current supplied to the DC motor can be simply regulated by simply adjusting the potentiometer, after that it changes the applied voltage at the gate terminal of the MOSFET. So we can control the speed of a DC motor by controlling the voltage at the gate terminal in the MOSFET. To increase the DC motor speed, we have to increase the applied voltage at the gate terminal of the MOSFET.

Here, the IRF540N MOSFET-based DC motor controller circuit was designed to control the speed of the motor. This circuit is very simple to design by using a MOSFET & a potentiometer. We can control the motor speed by simply controlling the applied voltage at the gate terminal of the MOSFET.

Advantages of MOSFETs for Motor Speed Control:

Transistors play a fundamental role in motor speed control circuits, and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are often favored over other types of transistors like BJTs (Bipolar Junction Transistors) and IGBTs (Insulated Gate Bipolar Transistors) for several reasons. In this article, we will explore the advantages and applications of using MOSFETs for motor speed control over other transistors.

  • High Efficiency:
    • MOSFETs exhibit very low on-resistance (RDS(on)), leading to minimal power dissipation and high efficiency in motor control circuits.
    • This high efficiency means less heat is generated, reducing the need for elaborate cooling systems, making MOSFETs suitable for high-power applications.
  • Fast Switching Speed:
    • MOSFETs have a very fast switching speed, typically in the nanosecond range.
    • This quick response allows for precise control of the motor’s speed and direction, making them suitable for applications where rapid changes are required.
  • Low Gate Drive Power:
    • MOSFETs require minimal gate drive power to switch between their on and off states.
    • This characteristic minimizes the power needed to control the transistor, resulting in energy-efficient motor control systems.
  • No Gate Current Required:
    • Unlike BJTs, MOSFETs do not require a continuous gate current to remain in their on-state, which reduces the control circuit’s power consumption.
    • This is particularly advantageous in battery-powered applications where energy efficiency is critical.
  • Temperature Tolerance:
    • MOSFETs can operate over a wide temperature range, making them suitable for both extreme cold and hot environments.
    • This feature is valuable in applications such as automotive systems and industrial machinery.
  • Reduced EMI:
    • MOSFETs generate less electromagnetic interference (EMI) compared to BJTs and IGBTs.
    • This is crucial in applications where EMI can interfere with nearby electronic devices or systems.

Applications of Motor Speed Control with MOSFETs:

  • Electric Vehicles (EVs) and Hybrid Vehicles:
    • MOSFETs are commonly used in the motor control systems of electric and hybrid vehicles.
    • They offer efficient and precise control over the electric motors, contributing to improved vehicle performance and range.
  • Industrial Automation:
    • In industries, MOSFET-based motor speed control is employed for conveyor belts, robotic arms, and other automated systems.
    • The rapid switching speed of MOSFETs ensures precise and responsive control in manufacturing processes.
  • Home Appliances:
    • MOSFETs are found in home appliances like washing machines, air conditioners, and fans for motor speed control.
    • Their efficiency and low heat generation make them ideal for energy-efficient appliances.
  • HVAC Systems:
    • Heating, Ventilation, and Air Conditioning (HVAC) systems utilize MOSFETs for controlling the speed of motors in fans and compressors.
    • This contributes to energy savings and precise temperature regulation.
  • Drone Propulsion:
    • Drones require efficient motor speed control to maintain stability and maneuverability.
    • MOSFETs are preferred in drone motor control circuits due to their low weight and high efficiency.
  • Computer Cooling Systems:
    • MOSFETs are used in computer cooling fans to adjust fan speed based on temperature, ensuring optimal cooling performance with minimal noise.
  • Electric Trains and Locomotives:
    • MOSFETs are employed in the motor control systems of electric trains and locomotives to regulate speed and direction efficiently.
  • Renewable Energy Systems:
    • Wind turbines and solar tracking systems use MOSFETs to control the speed of motors, optimizing energy generation.

In summary, MOSFETs offer numerous advantages for motor speed control, including high efficiency, fast switching speed, low gate drive power requirements, and reduced EMI. These advantages make them the preferred choice in a wide range of applications, from electric vehicles and industrial automation to home appliances and renewable energy systems. The versatility and reliability of MOSFETs make them a cornerstone of modern motor control technology.