What is an Oscillator?
Diode | Working Principle and Types of Diode
What is Zener Diode?
Application of Zener Diode
Vacuum Diode History Working Principle and Types of Vacuum Diode
p-n Junction Diode and Characteristics of p-n Junction
Full Wave Diode Rectifier
Half Wave Diode Rectifier
P-I-N Photodiode | Avalanche Photo Diode
LED or Light Emitting Diode
Tunnel Diode and its Applications
Full Wave Rectifiers
Op-amp | Working Principle of Op-amp
Amplifier Gain | Decibel or dB Gain
Integrated Circuits | Types of IC
Regulated Power Supply
Laser | Types and Components of Laser
Mobility of Charge Carrier
What are Photo Electrons?
Electron volt or eV
Energy Quanta | Development of Quantum Physics
Wave Particle Duality Principle
Heisenberg Uncertainty Principle
Schrodinger Wave Equation and Wave Function
Cyclotron Basic Construction and Working Principle
MOSFET | Working Principle of p-channel n-channel MOSFET
MOS Capacitor | MOS Capacitance C V Curve
Applications of MOSFET
Diode Bridge Rectifier
Theory of Semiconductor
Energy Bands of Silicon
Donor and Acceptor Impurities in Semiconductor
Conductivity of Semiconductor
Current Density in Metal and Semiconductor
Intrinsic Silicon and Extrinsic Silicon
P Type Semiconductor
N Type Semiconductor
P N Junction Theory Behind P N Junction
Forward and Reverse Bias of P N Junction
Hall Effect Applications of Hall Effect
Bipolar Junction Transistor or BJT | N-P-N or P-N-P Transistor Application Theory Biasing Amplifier
Applications of Bipolar Junction Transistor or BJT | History of BJT
Biasing of Bipolar Junction Transistor | BJT or Bipolar Transistor Biasing
JFET or Junction Field Effect Transistor
Questions on JFET or Junction Field Effect Transistor
DIAC Construction Operation and Applications of DIAC
Transistor as Switch
Application of Field Effect Transistor
Types of Transistors
Tunnel Diode and its Applications
The doping is very high so at absolute zero temperature the Fermi levels lies within the bias of the semiconductors. When no bias is applied any current flows through the junction.
Characteristics of Tunnel DiodeWhen reverse bias is applied the Fermi level of p - side becomes higher than the Fermi level of n-side. Hence, the tunneling of electrons from the balance band of p-side to the conduction band of n-side takes place. With the interments of the reverse bias the tunnel current also increases. When forward junction is a applied the Fermi level of n - side becomes higher that the Fermi level of p - side thus the tunneling of electrons from the n - side to p - side takes place. The amount of the tunnel current is very large than the normal junction current. When the forward bias is increased, the tunnel current is increased up to certain limit. When the band edge of n - side is same with the Fermi level in p - side the tunnel current is maximum with the further increment in the forward bias the tunnel current decreases and we get the desired negative conduction region. When the forward bias is raised further, normal p-n junction current is obtained which is exponentially proportional to the applied voltage. The V - I characteristics of the tunnel diode is given, The negative resistance is used to achieve oscillation and often Ck+ function is of very high frequency frequencies.
Tunnel Diode Symbol
Tunnel Diode ApplicationsTunnel diode is a type of sc diode which is capable of very fast and in microwave frequency range. It was the quantum mechanical effect which is known as tunneling. It is ideal for fast oscillators and receivers for its negative slope characteristics. But it cannot be used in large integrated circuits – that’s why it’s an applications are limited.
When the voltage is first applied current stars flowing through it. The current increases with the increase of voltage. Once the voltage rises high enough suddenly the current again starts increasing and tunnel diode stars behaving like a normal diode. Because of this unusual behavior, it can be used in number of special applications started below.
Oscillator circuits :Tunnel diodes can be used as high frequency oscillators as the transition between the high electrical conductivity is very rapid. They can be used to create oscillation as high as 5Gz. Even they are capable of creativity oscillation up to 100 GHz in a appropriate digital circuits.
Used in microwave circuits: Normal diode transistors do not perform well in microwave operation. So, for microwave generators and amplifiers tunnel diode are. In microwave waves and satellite communication equipments they were used widely, but now a day’s their uses is decreasing rapidly as transistor for working in wave frequency area available in market.
Resistant to nuclear radiation :Tunnel diodes are resistant to the effects of magnetic fields, high temperature and radioactivity. That’s why these can be used in modern military equipment. These are used in nuclear magnetic resource machine also. But the most important field of its use satellite communication equipments.
Tunnel Diode OscillatorTunnel diode can make a very stable oscillator circuit when they are coupled to a tuned circuit or cavity, biased at the centre point of negative resistance region. Here is an example of tunnel diode oscillatory circuit.
The tunnel diode is losing coupled to a tunable cavity. By using a short, antenna feed probe placed in the cavity off centre loose coupling is achieved. To increase the stability of oscillation and achieve o/p power over wider bandwidth loose coupling is used. The range of the output power produced is few hundred micro-watts. This is useful for many microwave application. The physical position of the tuner determining the frequency of operation. If the frequency of operation is changed by this method, that is called mechanical tuning. Tunnel diode oscillators can be tuned electronically also.
Tunnel diode oscillators which are meant to be operated at microwave frequencies, generally used some form of transmission lines as tunnel circuit. These oscillators are useful in application that requires a few millwatts of power, example- local oscillators for microwave super electrodyne receiver.