Diode Working and Types of Diode
Diode kitne prakar k hote hai ?
aur Diode ko kistarah se check
karte hai?
What is a Diode?
A diode is a device which only allows
unidirectional flow of current if operated
within a rated specified voltage level.
within a rated specified voltage level.
A diode only blocks current in
the reverse direction while the reverse voltage is within a limited
range otherwise reverse barrier breaks and the voltage at which this breakdown occurs is called
reverse breakdown voltage.
range otherwise reverse barrier breaks and the voltage at which this breakdown occurs is called
reverse breakdown voltage.
The diode acts
as a valve in the electronic and electrical circuit.
A P-N junction is the
simplest form of the diode which behaves as ideally short circuit when it is in forward biased
and behaves as ideally open circuit when it is in the reverse biased.
simplest form of the diode which behaves as ideally short circuit when it is in forward biased
and behaves as ideally open circuit when it is in the reverse biased.
Beside simple PN junction diodes, there are different types of diodes although
the
fundamental principles are more or less same. So a particular arrangement of diodes can
convert AC to pulsating DC, and hence, it is sometimes also called as a rectifier
fundamental principles are more or less same. So a particular arrangement of diodes can
convert AC to pulsating DC, and hence, it is sometimes also called as a rectifier
Symbol of Diode
The symbol of a diode is shown
below, the arrowhead points in the direction of
conventional current flow.
conventional current flow.
We can create a simple PN junction
diode by doping donor impurity in one portion
and acceptor impurity in other portion of silicon or germanium crystal block.
and acceptor impurity in other portion of silicon or germanium crystal block.
These make a p n junction at the
middle part of the block beside which one portion is
p-type (doped with trivalent or acceptor impurity), and another portion is n-type
(doped with pentavalent or donor impurity).
p-type (doped with trivalent or acceptor impurity), and another portion is n-type
(doped with pentavalent or donor impurity).
It can also be formed by joining a
p-type (intrinsic semiconductor doped with a
trivalent impurity) and n-type semiconductor (intrinsic semiconductor doped with a
pentavalent impurity) together with a special fabrication technique such that a p-n
junction is formed.
trivalent impurity) and n-type semiconductor (intrinsic semiconductor doped with a
pentavalent impurity) together with a special fabrication technique such that a p-n
junction is formed.
Hence, it is a device with two
elements, the p-type forms anode and the n-type forms
the cathode. These terminals are brought out to make the external connections.
the cathode. These terminals are brought out to make the external connections.
Working Principle of Diode
Unbiased Diode
N-side will have a significant
number of electrons, and very few holes (due
to thermal excitation) whereas the p side will have a high concentration
of holes and very few electrons. Due to this, a process called diffusion
takes place.
to thermal excitation) whereas the p side will have a high concentration
of holes and very few electrons. Due to this, a process called diffusion
takes place.
In this process free electrons
from n side will diffuse (spread) into the p
side and recombine with holes present there, leaving positive immobile
not moveable) ions in n side and creating negative immobile ions in p side
of the diode. Hence, there will be uncovered positive donor ions in n-type
side near the junction edge. Similarly, there will be uncovered negative
acceptor ions in p-type side near the junction edge.
side and recombine with holes present there, leaving positive immobile
not moveable) ions in n side and creating negative immobile ions in p side
of the diode. Hence, there will be uncovered positive donor ions in n-type
side near the junction edge. Similarly, there will be uncovered negative
acceptor ions in p-type side near the junction edge.
Due to this, numbers of positive
ions and negative ions will accumulate on
n-side and p-side respectively. This region so formed is called as
depletion region due to the “depletion” of free carriers in the region.
n-side and p-side respectively. This region so formed is called as
depletion region due to the “depletion” of free carriers in the region.
Due to the presence of these
positive and negative ions a static electric
field called as barrier potential is created across the pn junction of the
diode. It is called as "barrier potential" because it acts as a barrier and
opposes the further migration of holes and electrons across the junction.
field called as barrier potential is created across the pn junction of the
diode. It is called as "barrier potential" because it acts as a barrier and
opposes the further migration of holes and electrons across the junction.
Forward Biased Diode :
In a PN junction diode when the forward voltage is applied i.e. positive terminal of
a source is connected to the p-type side, and the negative terminal of the source
is connected to the n-type side, the diode is said to be in forward biased
condition. We know that there is a barrier potential across the junction.
This barrier potential is directed in the opposite of the forward applied voltage. So
a diode can only allow current to flow in the forward direction when forward
applied voltage is more than barrier potential of the junction.
This voltage is called forward biased voltage. For silicon diode, it is 0.7 volts.
For germanium diode, it is 0.3 volts.
When forward applied voltage is more than this forward biased voltage,
there will be forward current in the diode, and the diode will become short
circuited.
Hence, there will be no more voltage drop across the diode beyond this forward
biased voltage, and forward current is only limited by the
external resistance connected in series with the diode. Thus, if forward applied
voltage increases from zero, the diode will start conducting only after this voltage
reaches just above the barrier potential or forward biased voltage of the junction.
The time, taken by this input voltage to reach that value or in other words, the
time, taken by this input voltage to overcome the forward biased voltage is called
recovery time.
Reverse
Biased Diode
Now
if the diode is reverse biased i.e. positive terminal of the source is
connected to the n-type end, and the negative terminal of the source is
connected to the p-type end of the diode, there will be no current through the
diode except reverse saturation current.
This
is because at the reverse biased condition the depilation layer of the junction
becomes wider with increasing reverse biased voltage. Although there is a tiny
current flowing from n-type end to p-type end in the diode due to minority
carriers. This tiny current is called reverse saturation current.
Minority
carriers are mainly thermally generated electrons and holes in p-type
semiconductor and n-type semiconductor respectively. Now if reverse applied
voltage across the diode is continually increased, then after certain applied
voltage the depletion layer will destroy which will cause a huge reverse
current to flow through the diode. If this current is not externally limited
and it reaches beyond the safe value, the diode may be permanently destroyed.
This
is because, as the magnitude of the reverse voltage increases, the kinetic
energy of the minority charge carriers also increase. These fast moving
electrons collide with the other atoms in the device to knock-off some more
electrons from them. The electrons so released further release much more
electrons from the atoms by breaking the covalent bonds.
This
process is termed as carrier multiplication and leads to a considerable
increase in the flow of current through the p-n junction. The associated
phenomenon is called Avalanche Breakdown
Types of Diode
The types of diode are as follows :
1.
Zener diode
2.
P-N junction diode
3.
Tunnel diode
4.
Varactor diode
5.
Schottky diode
6.
Photo diode
7.
PIN diode
8.
Laser diode
9.
Avalanche diode
10.
Light emitting diode.
WATCH OUR REPAIRING VIDEOS ON
OUR YOUTUBE CHANNEL.
ALL MOBILE REPAIRING TOOLS &
THEIR PRICES IN MARKET.
LIKE SHARE SUBSCRIBE OUR CHANNEL.
WATCH OUR REPAIRING VIDEOS ON
OUR YOUTUBE CHANNEL.
ALL MOBILE REPAIRING TOOLS &
THEIR PRICES IN MARKET.
LIKE SHARE SUBSCRIBE OUR CHANNEL.
0 comments:
Post a Comment
Meri website per aap apna feed back zaroor de apka feed back mere liye bahut important hai q k apki opinion se mai aur achi service de paunga thank you friends....