impatt diode
TRANSCRIPT
IMPATT DIODE
“Be A Diode To Remove Negative Thinking”
GROUP MEMBERS
SALEEM SHAHID FA07-BET-143
MUHAMMAD MAJID FA07-BET-098
MUHAMMAD RIZWAN FA07-BET-104
OVERVIEW
PHYSICAL STRUCTURE
PRINCIPLE OF OPERATION
APPLICATIONS
PERFORMANCE
DIFFERENCE BETWEEN IMPATT AND ORDINARY DIODE
IMPATTThe word IMPATT stands for IMPact Avalanche Transit Time
The IMPATT diode is an RF semiconductor device that is used for generating microwave radio frequency signals
Mostly used in high-frequency electronics and microwave devices
Form of high power diode
PHYSICAL STRUCTUREp+nin structure
a) Avalanche Region or injection region
b) Drift Region
PHYSICAL STRUCTUREN-type layer is around one or two microns thick.
The intrinsic layer between 3 and 20 microns.
At High frequencies intrinsic will be more thinner.
For Fabrication we use silicon, gallium arsenide, germanium and indium phosphide.
Mounted in microwave packets to ensure that performance is not impaired by substandard packages.
CLASSIFICATIONTypes of Impatt diodes are:-
1. Single drift region (SDR)
2. Double drift region (DDR)
3. Double avalanche region (DAR)
Intentionally Left Blank
PRINCIPLE OF OPERATIONImpact ionization of atoms
Avalanche multiplication of electrons
Transit time effect
PRINCIPLE OF OPERATIONThe Avalanche or Injection RegionRegion with relatively high doping and high field, Avalanche multiplication occurs here
Drift RegionRegion with essentially intrinsic doping and constant field where the carriers move across the diode taking a certain amount of time dependent upon its thickness
PRINCIPLE OF OPERATIONThe IMPATT diode is operated under reverse bias conditions (No current flows ideally)
Current flows due to breakdown caused by avalanche multiplication of electrons
The electric field at the p-n junction is very high because the voltage appears across a very narrow gap creating a high potential gradient
PRINCIPLE OF OPERATIONAn AC voltage superimposed on the dc is applied
If sufficient then free electron liberate an electron from the covalent bond this process can cascade (avalanche) very quickly into chain reaction producing a number of electrons
Impact avalanche
PRINCIPLE OF OPERATIONAvalanche region introduces a 90o phase shift between the ac signal and the electron concentration in this region
Length of the drift region equal to the wavelength of the signal then additional phase shift of 90o between the ac voltage and the diode current
ADVANTAGE
High Power Capability
Negative Resistance
DISADVANTAGEHigh input voltageHigh level of phase noiseLess efficiency (40%)
Noise - Microwave Devices
0.05.0
10.015.0
20.025.030.035.0
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IMP
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Devices
Noise Figurein dB
Intentionally Left Blank
IMPATT I-V Characteristics
0 T/2 T 3T/2 2T 5T/2 Iinj
t0 T/2 T 3T/2 2T 5T/2
VDC
V
t
vAC
rAC<0
PAC=IV
COMPARISONImpatt is designed for high power applications whereas, a diode burns (heat-up) at high power
Impatt is operated at reverse bias whereas a diode is normally operated at forward bias because at reverse bias there is high voltage drop
APPLICATIONSIMPATT diodes are ideal where small cost effective microwave radio sources are needed
The main application for IMPATT diodes is in microwave generators
Used in high-frequency electronics and microwave devices
APPLICATIONSBest performance at frequencies extending into the mm-wave range
The negative resistance property of IMPATT diode can be used in oscillator
The stable region of operation can be used to amplify the RF signals
IMPATT diodes give more output power
APPLICATIONSLow power RADAR transmitters may use an IMPATT diode as a power source
They can be fabricated with Si, GaAs, and InP
Used in a variety of applications from low power radar systems to alarms, radios
APPLICATIONSIt is also used in applications where phase noise performance is unlikely to be of importance
THANK YOU FOR YOUR PATIENCE!!