Mosfet Switch: How to use Mosfet as a switch

As we all know, a Electronic Switch is a device which has two states, ON and OFF. Similarly, we can implement a switch with the help of Mosfet. As we all know a Mosfet has 3 states, Ohmic, Saturation and Cutoff states. We can operate mosfet in Cutoff and Saturation state of Mosfet to help it work as a Switch. A Mosfet switch when acted upon gate supply above minimum threshold works as ‘ON’ and when there is no gate supply it works as a “OFF”. Let us study about How to use Mosfet as a Switch.

Circuit Diagram: Mosfet as a Switch.

Mosfet switch: How to use Mosfet as a Switch
Mosfet as a Switch
  • The circuit implementation is simple. We require only few components.
  • A 12V DC supply is connected to the gate of the Mosfet through a push button switch.
  • A LED is connected as our Load. We can connect other peripherals too.
  • We are connecting a resistor R1 so that in a situation of zero gate supply there is no unwanted voltage at the gate terminal.
  • The Push button helps us to connect and disconnect the gate supply.


ON State:

ON state
ON state- Mosfet as a switch
  • When we push the Push button, the 12v supply gets connected to the gate terminal of the Mosfet.
  • Therefore, the Mosfet gets ‘ON’ and it starts conducting. Hence the current starts flowing which makes the LED glow.
  • In simple explanation, the LED gets connected to ground as Mosfet turns ON and it starts glowing. Its anode voltage will be 12V and cathode will be connected to the ground.
  • Hence, in this condition the Mosfet works as a ON switch.

OFF State:

Off state: Mosfet as a Switch
Off state: Mosfet as a Switch
  • Now we disable the Push button. Therefore, the 12V supply gets disconnected to the gate of the mosfet.
  • The mosfet turns off.
  • The led’s cathode terminal gets disconnected from the ground.
  • Hence, it stops glowing.
  • No current Id flows now.

This is how mosfet switch works.

Check out this video of How to use Mosfet as a switch which gives implementation of DC Motor in place of LED.

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