Power MOSFET Motor Control

Because of the very high input gate resistance of MOSFETs, MOSFET’s fast switching speeds, and the ease at which they can be driven makes them ideal to interface with op-amps or standard logic gates. Nevertheless, care must be taken to ensure that the gate-source input voltage is correctly chosen because when using the MOSFET as a switch the device must obtain a low R_DS(on)channel resistance in proportion to this input gate voltage.

Power MOSFET can be used to control the movement of DC motors or brushless stepper motors directly from computer logic or Pulse-width modulation (PWM) type controllers. Because a DC motor offers high starting torque that is also proportional to the armature current, MOSFET switches along with a PWM can be used as a very good speed controller that would provide smooth and quiet motor operation.

A Simple Power MOSFET Motor Controller

As the motor load is inductive, a simple “Free-wheeling” diode is connected across the load to dissipate any back emf generated by the motor when the MOSFET turns it “OFF”. The Zener diode is used to prevent excessive gate-source input voltages.

You can also read: The Junction Field Effect Transistors (JFET)

John Mulindi

John Mulindi is an Industrial Instrumentation and Control Professional with a wide range of experience in electrical and electronics, process measurement, control systems and automation. In free time he spends time reading, taking adventure walks and watching football.