The Gunn Diode

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Introduction

-What is Gunn Diode?
The Gunn diode is used as local oscillator covering the microwave frequency range of 1 to 100GHz
-How Gunn Diode works?
By means of the transferred electron mechanism, it has the negative resistance characteristic
-What s the applications?
Local Oscillator and Avoid Collision Radar instead of Klystron etc..
-What s the advantages?
Low noise, High frequency operation and Medium RF Power

Gunn Effect

Gunn effect was discovered by J.B Gunn in IBM : 1963
Above some critical voltage, corresponding to an electric field of
2000 4000 V/cm, the current in every spectrum (GaAs) became a
fluctuating function of time

The current waveform was produced by applying a voltage pulse of 59V
And 10ns duration
Oscillation frequency was 4.5Ghz
The period of oscillation is equal to the transit time of electrons through the device

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Gunn Diodes

Gunn diodes are used as transferred electron oscillators (TEO) by using the negative resistance property of bulk Gallium Arsenide. The figure below shows the electron velocity in GaAs as a function of the applied electric field. Greater than about an electric field of 3.2 KV/cm, the electrons in N type GaAs move from a high-mobility, lowenergy valley to another valley where the mobility is lower. Consequently, the net electron velocity is lower. This negative resistance is used for generation of microwave power.