Date post: | 26-Oct-2014 |
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MICROWAVE SOLID STATE DEVICES
RIDLEY WATKINS HILSUM THEORY
The separation between the bottom of the lower valley and the bottom of upper valley must be greater than 0.026 eV.
Electrons in the lower valley must have high mobility,small effective mass, low density where as the upper valley must have low mobility,large effective mass and high density
Separation energy between the valleys must be smaller than the gap energy b/w conduction & valence bands
Two most useful semiconductors Si,Ge do not meet all these criteria So GaAs,InP,CdTe do satisty these
criteria
GUNN DIODE
GUNN DIODE
Eq-ckt
a)fL=10^7cm/sec,b) fL<10^7cm/sec,c) fL>2*10^7cm/sec
LSA Mode
Oscillations builds up when the –ve resistance of the gunn diode equals to the load resistance.
The peak to peak amplitude of the oscillations are approximately equal to the voltage range in the –ve resistance region
Impatt Diode(impact ionization avalanche transit time)
Trapatt Diode(trapped plasma avalanche triggered transit time)
Tunnel diode