The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a semiconductor device that is widely used for amplifying and switching electronic signals. If we want to operate MOSFET as switches, they should be biased in such a way that they alter between saturation and cut-off states.
This is because, in the saturation region, there is a constant amount of current flowing through the device, while in the cut-off region, there will be no current flowing through the device, just mimicking the behavior of a closed and open switch, respectively.
Hardware Components:
Following are the necessary hardware items required to use MOSFET as a switch::
Working Explanation
To use a MOSFET as a switch, you have to make its gate voltage (Vgs) higher than the source voltage. If you connect the gate to the source or both the voltages are equal (Vgs=0) then the MOSFET will turn off. In this circuit, we have connected the drain terminal to VCC by using a resistor and LED. The source terminal is connected to the ground. And to the gate terminal, we have connected a logic state, which will continuously switch the input applied to the gate between High and Low.
To start the simulation press the play button located at the bottom of the window. To change the input at the gate, click the logic state symbol and it will switch its state between High and Low. You can also connect a pulse generator to the gate if you want the state to change automatically.
Connections
- Open the Proteus software and select the required components from the library.
- Place a resistor and LED in between the positive terminal of the battery and the Drain terminal of MOSFET.
- Connect the Source terminal of MOSFET to GND
- Connect the Logicstate to the Gate terminal of MOSFET.
- Now, start the simulation and test the circuit.
Application
- MOSFET can be used to switch a high power device from a microcontroller since high power device cannot be controlled directly from the microcontroller.
Circuit Diagram
