SEMICONDUCTOR DIODE
The name Diode comes from the fact that it has
two Electrodes Anode & Cathode. Originally the Diode was in the form of a
vacuum Tube.
Some drawbacks of vacuum tube Diode.
- · Uses high voltage between plates (A) and cathode(K) [100v to 200v]
- · The filament requires separate power supply (6V) to generate electrons by thermionic emission.
- · Too Bulky and produces a lot of heat.
The above mentioned problems leads to what we
have now a days i.e. SEMICONDUCTOR
DIODE. It is Unidirectional Device Allow current only in one direction.
The current they pass is depend on the voltage between the lead. It does not obey ohms law.
Dynamic resistance is most important parameter
of semiconductor i.e. it offer different resistance in highly doped region as
well as in lightly doped region.This Dynamic resistance is useful in wave
shaping of signal (i.e. rectifiers converting ac to dc), used as voltage
regulator and as switches in some application.
Ordinary Diodes can be split into two diodes.
1.
Signal diodes:
Which passes only small amount of current through it.
2.
Rectifier diodes:
Which passes large amount of current through it.
In addition to these there are
LEDs and Zener diodes.
- The first diode in the fig is a small signal diode like 1N914 type commonly used in Switchingapplication.
- Second one in the above fig is a Zener diode used in regulator application.
- Third one is a Varactor diode used in FM modulation.
- Fourth one is Vacuum tube diode that is totally replaced by Semiconductor diode. Its is used in CRO type Television.
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