A tunnel diode, also known as an Esaki diode, is a specialized type of diode that exhibits a phenomenon called "tunneling effect." It was first invented by Leo Esaki in 1958, for which he received the Nobel Prize in Physics in 1973. Tunnel diodes are unique in their ability to provide negative resistance, making them useful in specific applications.
Here are some key characteristics and features of tunnel diodes:
Tunneling effect: The tunneling effect is the principle behind the operation of tunnel diodes. It occurs when electrons can pass through a potential barrier, even though their energy levels are lower than the barrier's height. This effect allows current to flow through the diode even when it is reverse biased.
Negative resistance: Unlike conventional diodes, tunnel diodes exhibit a negative resistance region in their voltage-current characteristic curve. This means that as the voltage across the diode increases, the current flowing through it decreases. This unique characteristic enables tunnel diodes to be used in oscillator circuits, amplifiers, and switching applications.
Fast switching speed: Tunnel diodes have extremely fast switching speeds due to their ability to transition between high and low current states rapidly. This makes them suitable for applications that require high-frequency operations.
Low power consumption: Tunnel diodes are known for their low power consumption, which makes them suitable for low-power electronic circuits.
Limited voltage range: Tunnel diodes have a limited voltage range of operation, typically ranging from a few millivolts to a few hundred millivolts. They are not designed for high-voltage applications.
Applications: Tunnel diodes find application in various electronic circuits, such as oscillators, amplifiers, high-frequency signal generators, microwave circuits, and ultra-high-speed switching applications. They are also used in some specialized areas, including digital logic circuits, computer memory cells, and radar systems.
It's worth noting that tunnel diodes are less commonly used in modern electronic devices compared to other diode types due to the development of other semiconductor technologies. However, they still hold importance in specific applications where their unique characteristics are beneficial, such as in high-frequency and low-power circuits requiring fast switching speeds.