Contents
Which is more complicated a MOSFET or a switch?
Even though transistors get used for switching applications, they are much more complicated than a switch. In the case of MOSFETs, they have three regions you need to understand: cut-off, linear and saturation. In the cut-off region, there is no current flowing between the drain and source.
Are there any myths or misconceptions about MOSFETs?
A minor point with a subtle difference, but a common MOSFET misconception. In this post, I dispel that and other common myths and misconceptions around using MOSFETs. As with all engineering tips and tricks, this post is not a definitive guide to FETs.
What’s the difference between a BJT and a MOSFET?
MOSFETs and BJTs define their saturation region differently! A MOSFET acts as a variable resistor in the linear region and as a current source in the saturation region. Unlike a BJT, to use a MOSFET as a switch, you need to operate within the linear region. (BJT switches operate in their saturation region.)
When does the MOSFET become a variable resistor?
If the drain current is constant at 10 A, then varying Vgs will cause the drain-source voltage drop to change. In other words, the MOSFET is a variable resistor when operated in the linear region. The next region is called the saturation region.
Why does no current flow into the MOSFET?
Because of the isolation of the Gate there is no current flow into the MOSFET from Gate. When voltage is applied at the gate, it changes the width of the Drain-Source channel along which charge carriers flow (electron or hole). The wider the channel, the better the device conducts.
What should the resistor be on a MOSFET?
You should also have a resistor in series with the Arduino output to limit the current, since the gate is highly capacitive and can draw a big instantaneous current when you try to turn it on. Around 220 ohms is a good value. This page shows some detail explanation how a MOSFET works as a switch.
What do you need to know about n channel MOSFET?
N-Channel – For an N-Channel MOSFET, the source is connected to ground. To turn the MOSFET on, we need to raise the voltage on the gate. To turn it off we need to connect the gate to ground.