MESFET Advantages and Disadvantages

This page covers the advantages and disadvantages of MESFETs (Metal-Semiconductor Field-Effect Transistors). It highlights the benefits and drawbacks of using MESFETs in various applications.

What is a MESFET?

Introduction: MESFET stands for Metal-Semiconductor Field-Effect Transistor. It’s a type of FET derived from a metal-semiconductor Schottky barrier diode.

GaAs MESFETs are often preferred over silicon devices because GaAs provides higher electron mobility, a higher electric field, and a higher electron saturation drift velocity.

Figure 1: MESFET Structure

GaAs MESFETs are commonly used as microwave integrated circuits in broadband amplifiers. The structure of a typical MESFET is shown in Figure 1.

The working principle of a MESFET is similar to that of a JFET, but the MESFET only has one depletion region, whereas a JFET uses two. The source-gate junction is kept in reverse bias, while the source-drain is kept in forward bias.

Refer to MESFET vs JFET vs MOSFET for more details.

Benefits or Advantages of MESFET

The following are the benefits or advantages of using MESFETs:

• They offer much better noise figures at microwave frequencies.
• They deliver high power output.
• GaAs MESFETs offer high electron mobility, a higher electric field, and a higher electron saturation drift velocity compared to silicon MESFETs.
• They offer a high transit frequency.

Drawbacks or Disadvantages of MESFET

The following are the disadvantages of MESFETs:

• The MESFET structure includes a Schottky metal gate. This limits the forward bias voltage on the gate to the turn-on voltage of the Schottky diode, which is typically 0.7V.
• Due to the above reason, the threshold voltage must be less than the turn-on voltage. Therefore, it’s difficult to fabricate circuits that use a large number of enhancement-mode MESFETs.