How a PN Junction Diode Works

summary of the basics or a tutorial of how a PN junction or diode works showing how does the current flow in only one direction, and how diodes can be used on their own and in transistors

Before reading this page, it is worth reading the page entitled "What is a semiconductor" - see the related articles list below the left menu. This will explain some of the basics of semiconductors and some of the terms used on this page.

The PN junction is one of the most important structures in today's electronics scene. It forms the basis of today's semiconductor technology, and was the first semiconductor device to be used. The first semiconductor diode to be used was the Cat's Whisker wireless detector used in early wireless sets. It consisted of a wire placed onto a material that was effectively a semiconductor. The point where the wire met the semiconductor then formed a small PN junction and this detected the radio signals.

The diode or PN junction was the first form of semiconductor device to be investigated in the early 1940s when the first real research was undertaken into semiconductor technology. It was found that small point contact diodes were able to rectify some of the microwave frequencies used in early radar systems and as a result they soon found many uses.

Today, the PN junction has undergone a significant amount of development. Many varieties of diode are in use in a variety of applications. In addition to this, the PN junction forms the basis of much of today's semiconductor technology where it is used in transistors, FETs, and many types of integrated circuit.

The PN junction is found in many semiconductor devices today. These include:

• Diode
  
  
• Bipolar transistor
  
  
• Junction FET
  
  
• Diac
  
  
• Triac
  

The PN junction has the very useful property that electrons are only able to flow in one direction. As current consists of a flow of electrons