MOSFET Transistors

Switch or amplify a signal with a high-quality MOSFET transistor. Designed to change conductivity in higher-current applications, these transistors are suitable for a range of settings, from technological and automotive to domestic.

If you are searching for MOSFET transistors, whether you want an N-channel or P-channel MOSFET to complete your circuit, you will find it here at RS. We have over 200 products in stock, and these are all made to the highest standards by trusted manufacturers.

Read on to find out more about MOSFET transistors.

What are MOSFET transistors?

MOSFET transistors - metal-oxide semiconductor field-effect transistors - are one of the most used transistors. MOSFETs are used for switching or amplifying signals, and they are voltage-controlled. This is achieved by altering the conductivity in relation to the level of the voltage that's applied.

The voltage present defines how conductive the device is. The more conductive the device, the higher the amount of voltage applied through the MOSFET.

The difference between FET and BJT

There are two common types of transistors: the Bipolar Junction Transistor (BJT) and the Field Effect Transistor (FET). The major difference between BJT and FET is that only the majority charge carries flow in a FET, whereas in BJT, both majority and minority charge carriers flow.

Additionally, BJTs are current controlled and FETs are voltage controlled. This means that BJTs are most often found in electrical currents that have up to one amp, while FETs are used for more robust applications. MOSFET transistors are a type of FET, and they are used in applications that have a higher current.

How do MOSFET transistors work?

A MOSFET transistor has four terminals: the source, gate, drain and body. In many cases, the body terminal is connected to the source, taking the number of terminals down to three. The terminals control the flow of the electrical current between the source and the drain.

The width of the channel is controlled by the voltage on the gate terminal. This is located between source and drain. How the MOSFET transistor functions depends on how the electrical variation occurs in the channel width and the flow of the carriers. The charge enters through the source and exits via the drain.

Different types of MOSFET transistors

There are different types of MOSFET transistor. In terms of their operational mode, there are two types: enhancement and depletion. There are further variations within these two types.

• Enhancement mode

There is no conduction at zero voltage when using enhancement mode. This means that the transistor is closed or set to "off" as there's no channel. This changes then the gate voltage is increased above the source voltage. Here, the charge carriers, which are known as holes, are moved, leaving the electrons and a wider channel.

The gate voltage moves with the current, so as the gate voltage increases, the current increases and the reverse is also the case.

• Depletion mode

Here, the channel is already formed and the conduction occurs even at zero voltage. Unlike enhancement mode, it is open - or "on" - by default. The channel here is drained of charge carriers and this reduces the width of the channel.

Whereas the gate voltage is directly proportional to the current in enhancement mode, here the opposite is the case. The gate voltage increases as the current decreases and vice versa.

Within these two categories, there are also N-channel MOSFETs and P-channel MOSFETs:

• N-channel MOSFETs

This MOSFET has an N-channel region between the source and drain. The drain and source are heavily doped n+ region, while the body is P- type.

• P-channel MOSFETs

The P- channel MOSFET has a P- channel region between the source and drain terminals. The drain and source are heavily doped p+ region and the body is n- type. The flow of current moves in the direction of positively charged holes.

Power MOSFETs

It's worth noting the power MOSFET. This is set out in a vertical composition and is designed to allow the transistor to simultaneously deliver high blocking voltage and high current.

Where can MOSFETs be used?

MOSFET transistors are used to switch or amplify electrical signals. Therefore, they are best suited to digital circuits, such as memory chips or microprocessors. They're also found in calculators, digital wristwatches and analogue switches, as well as the automotive industry in power converters in electric vehicles.

Where to buy MOSFET transistors

Whether you need a MOSFET transistor replacement or you're creating a MOSFET circuit and need the right transistor for the task, choose RS. You'll find that we are an authorized, North America-based distributor of MOSFET transistors, along with other types of transistors, and we work with leading names in the industry, including Siliconix / Vishay, Diodes Inc, and Infineon. We proudly bring you a range of high-quality products that meet the highest standards.

If you have any questions, we are on hand to help. Get in touch with the team today. You can also find advice and tips in our expert content hub.