OBJECTIVE
 Objective of this practical is to learn about diode and
identify its terminals
Some Concept Regarding Diode
 What is Diode
 Diode is a two terminal doped semiconductor device
with ability to conduct current only in one direction
after a certain amount of voltage called barrier
potential is applied to it in a proper way. Diode is one
of great invention which is used in many applications
such as rectifier circuits, voltage limiter circuits,
voltage clamper circuits, voltage multiplier circuits etc.
SYMBOL OF DIODE
How
Diode
is
made?
 Diode is made by Combination of P and N-Type
semiconductor
 Boundary between P and N-Type semiconductor is
called PN Junction
What are P-type and N-type
Semiconductor Materials?
N-type Semiconductor
 When




we add a pentavalent impurity to pure
semiconductor we get n-type semiconductor.
Arsenic atom has 5 valence electrons.
Fifth electron is superfluous, becomes free electron and
enters into conduction band.
Therefore pentavalent impurity donates one electron and
becomes positive donor ion.
Pentavalent impurity known as donor.
As
N-type
Pure
Si
si
P-type Semiconductor
 When we add a Trivalent impurity to pure semiconductor we get





p-type semiconductor.
Gallium atom has 3 valence electrons.
It makes covalent bonds with adjacent three electrons of silicon
atom.
There is a deficiency of one covalent bond and creates a hole.
Trivalent impurity accepts one electron and becomes negative
acceptor ion.
Trivalent impurity known as acceptor.
Ga
P-type
Pure
Si
si
Coming Towards Objective Now
 Required Apparatus for Obtaining Objective are
Few diodes, breadboard, multimeter, connecting wire
etc.
Procedure
Three Methods to be Followed
 Method 01: Physical shape
 Method 02: Using Multimeter (Ohm meter)
 Method 03: Using diode option on Multimeter
Method 01: Physical shape
 Diode is marked with a color band on one of its two sides
and that colored side identifies negative terminal
(cathode) of a diode. Where K represents cathode or
negative terminal of a diode and A represents anode or
positive terminal of diode
Method 02: Using Multimeter (Ohm meter)
 First select Ohmmeter in Multimeter
 if internal resistance of diode is in the range of kilo
ohms, then the terminal of diode which is connected
with the positive of ohm meter is called anode and
other terminal will be called cathode.
 if internal resistance of diode is in the range of mega
ohms, then the terminal of diode which is connected
with the positive of ohm meter is called cathode and
other terminal will be called anode.
Method 03:Using diode option on
multimeter
 if multimeter shows 0.7 volt then the terminal of
diode which is connected with positive of multimeter
is called anode and other terminal will be called
cathode as shown in fig(a).
 if multimeter shows 2.60 volt then the terminal of
diode which is connected with positive of multimeter
is called cathode and other terminal will be called
anode as shown in fig(b).
 Fig(a) & Fig(b) Shown in Next Coming Slide
ANY QUERY?