Mosfets like bjts can function as electronic switches.
P channel mosfet power switch circuit.
This is a simple circuit where a n channel enhancement mode mosfet will turn on or off a light.
This tutorial will explore the use of a p channel and n channel mosfets as a power switch and general transistor theory.
Although unlike bjts mosfets are turned on not by current but by voltage.
2 p channel opto isolated mosfet switching circuit using irf9630 fig.
Mosfet as a switch.
This is for use with 5 volt micro controllers such as arduino.
Notice the similarities and differences between figs.
An excellent use for p channel is in a circuit where your load s voltage is the same as your logic s voltage levels.
To turn on the n channel mosfet requires a positive gate source voltage whereas the p channel mosfet requires a negative gate source potential.
We require only few components.
The circuit implementation is simple.
In this project we will go over how to connect an p channel mosfet to a circuit for it to function as an electronic switch.
In this case use a p channel mosfet to turn the relay on from the arduino s i o pin.
This switch will operate on the positive side of a power supply with a negative common.
Assume the device is initially off.
Mosfets are voltage controlled devices.
The current necessary for the relay coil is too high for an i o pin but the coil needs 5v to work.
If you are new and unaware about the working of a n channel mosfet check out this article.
Mosfet as a switch.
There are a variety of configurations for driving the two mosfets with many different applications.
2 shows how to use a p channel irf9630 mosfet to switch the positive side of the power supply to the light bulbs acting as a load.
The type of p channel mosfet we will use is the enhancement type mosfet the most commonly used type of mosfet.
A 12v dc supply is connected to the gate of the mosfet through a push button switch.
A circuit for a typical high side switch using a p channel mosfet is shown in fig.
For example if you re trying to turn on a 5 volt relay with an arduino.
We will understand the operation of a mosfet as a switch by considering a simple example circuit.
The input opto coupler and q1 operate the same as fig.
Firsly in fig 4 6 13 the resistor r4 whose purpose is to discharge any remaining potential on the gate at switch off is now connected to the positive supply rail instead of to ground.
During switching a mosfet s source voltage must remain fixed as any variation will modulate the gate and thus adversely affect performance.