PRACTICAL # 01

Diode and its terminal identification. By: Engr.Irshad Raheem Memon

OBJECTIVE

Objective of this practical is to learn about diode and identify its terminals

Some Concept Regarding DiodeWhat 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 semiconductorBoundary between P and N-Type

semiconductor is called PN Junction

What are P-type and N-type Semiconductor Materials?

N-type SemiconductorWhen 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 Puresi

N-typeSi

P-type SemiconductorWhen 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.

GaPuresi

P-typeSi

Coming Towards Objective NowRequired 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?