IMPATT Diode: Advantages and Disadvantages

This page covers the advantages and disadvantages of an IMPATT diode, outlining its benefits and drawbacks.

What is an IMPATT Diode?

Introduction: An IMPATT diode is a two-terminal semiconductor negative conductance device.

It operates based on two key phenomena:

• Avalanche multiplication
• Transit time effects

“IMPATT” stands for Impact Ionization Avalanche Transit Time. It is essentially an improved version of the Read diode. IMPATT diodes are often made from silicon carbide due to its higher breakdown field.

Figure 1: IMPATT diode structure

The figure above depicts the structure of an IMPATT diode, which typically consists of a p⁺ - n - n⁺ configuration.

• The junction between p⁺ and n is called the avalanche region.
• The n⁺ region is known as the drift space.

IMPATT devices with two drift regions are also available.

Applications of IMPATT Diode

The IMPATT diode finds use in various applications, including:

• Modulated output oscillator
• Microwave Generator
• Receiver LO (Local Oscillator)
• Parametric Amplifier
• Intrusion alarm network
• FM telecommunication transmitters
• CW Doppler radar transmitter

Benefits or Advantages of IMPATT Diode

The following are the benefits or advantages of IMPATT diodes:

• Operates from 3 to 100 GHz frequency range.
• It has high power capabilities compared to other microwave diodes.
• Its output is more reliable compared to other microwave diodes.
• It acts as a narrow band device when used as an amplifier.
• It can be used as excellent microwave generators.
• It can produce carrier signals for microwave transmission systems.

Drawbacks or Disadvantages of IMPATT Diode

Here are the disadvantages of IMPATT diodes:

• It has a high noise figure due to the avalanche process and higher operating current. Shot noise is generated within the device due to this high operating current. Typically, the noise figure of an IMPATT diode is about 30 dB.
• It produces spurious noise (AM and FM) at higher levels compared to klystron and Gunn diodes.
• The tuning range of an IMPATT diode is not as good as that of a Gunn diode.
• It offers lower efficiency compared to a TRAPATT diode.