HEXFET vs MOSFET: Understanding the Key Differences

This page compares HEXFET and MOSFET and highlights the differences between them.

MOSFET structure and symbol

The full form of MOSFET is Metal Oxide Semiconductor Field Effect Transistor.

Figure-1 depicts a 600 Volt SJ-MOSFET structure and circuit symbol.

HEXFET structure

HEXFET is a trademark of power MOSFET developed by International Rectifier.

The HEXFET structure is shown in figure-2. As shown, the silicon oxide layer between the gate and source regions can be punctured by exceeding its dielectric strength. The symbol is the same as a power MOSFET, as shown in figure-1. It is a voltage-controlled power MOSFET device.

When a voltage is applied between the Gate and Source terminals, an E-field is established within the HEXFET device. This electric field inverts the channel from P to N, allowing current to flow from Drain to Source in an uninterrupted sequence of N-type silicon.

FETs can be of two types: enhancement mode and depletion mode.

Enhancement mode devices require a gate voltage of the same sign as the drain voltage in order to pass current.

Depletion mode devices are usually ON and are turned OFF by a Gate voltage of the same polarity as the drain voltage.

The following points differentiate HEXFET from MOSFET devices:

• All HEXFET® devices are enhancement mode devices.
• As mentioned, HEXFET® is a trademark of International Rectifier.
• The gate-to-source voltage of most HEXFET devices is between 10 and 30 V.
• Example: IRF540 is a HEXFET device and IRL540 is a MOSFET device.