Tunnel diode basics

Tunnel diode is one of the many microwave semiconductor devices in use today. This page covers Tunnel diode basics and its applications.

The tunnel diode operates on tunneling principle which is a majority carrier event. There are few conditions which ensures high tunneling probability.
•  thin depletion zone
•  heavy doping of semiconductor material
There should be filled and empty energy state for each tunneling carrier.

tunnel diode equivalent circuit
Fig:1 Tunnel Diode Equivalent Circuit

From the tunnel diode equivalent circuit it is imperative that tunnel diode oscillates when total reactance is zero and negative resistance balance out the series resistance. There are two type of frequencies equations for which are mentioned below.

Resistive Frequency, Fr (Hz) = (1/2*pi*R*Cj)*((R/Rs)-1)0.5

Self resonant Frequency Fs (Hz) = (1/2*pi) ((1/LsCj) - (1/(RCj)2))0.5

Where in,
R is the absolute value of negative resistance (Ohms)
Rs is the series resistance (Ohms)
Cj is the junction capacitance (Farads)
Ls is the series inductance (Henrys)

Tunnel Diode Applications

Tunnel diode is used as an amplifier, as one shot multivibrator and as as oscillator.

Difference between Tunnel diode and normal p-n junction diode

Refer tunnel diode vs p-n junction diode

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Tunnel Diode calculator

Tunnel diode calculator

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