Practical things about Diodes

In this topic we shall see about the practical things about diode. When we use diode in different practical circuits we always require to note these points. So I recommend you to perform the given steps in this topic as a part of practical experimentation.

Aim: To study the basic concepts of PN junction diode.

Apparatus: different types of diodes, multimeter, connecting wires, etc.

Connection Diagram

How to check diode using a DMM or AMM

Basic First!

1. A diode contains two semiconductor layers known as p-layer and n-layer.
2. A diode has two terminals ANODE and CATHODE.
3. It has one junction known as p-n junction. It also acts as potential barrier for the diode.
4. Any diode conducts current only in one direction i.e. from ANODE to CATHODE. Hence it is called unidirectional device.
5. When current flows through a Silicon diode, its voltage drop = 0.6V to 0.7V.
6. When current flows through a Germanium diode, its voltage drop = 0.2V to 0.3V.
7. If two Silicon and/or Germanium diodes are in series, their voltage drops ADD TOGETHER.
8. When two or more Silicon diodes are in parallel, their total voltage drop = 0.6V or 0.7V.
9. If two or more Germanium diodes are in parallel, their total voltage drop = 0.2V or 0.3V.
10. When a number of Silicon and Germanium diodes are connected in parallel, their total voltage drop is equal to the voltage drop of a SINGLE GERMANIUM DIODE.

Procedure

Follow the procedure step by step and write down your observations –

Finding the anode and cathode of diode

1. Take a multimeter and put it in ohmmeter range.
2. RED probe is positive and BLACK probe is negative.
3. Connect two probes to two terminals of diode, AT RANDOM.
4. If the multimeter DOES NOT DEFLECT, reverse the probes connections.
5. Now if the multimeter deflects, the terminal connected to RED probe is anode.
6. And the terminal connected to BLACK probe is cathode.
7. Mark the either anode and cathode of the diode under test by slightly bending its one terminal.

Checking the diode for OK or Faulty condition

1. Take a multimeter and put it in ohmmeter range.
2. Condition 1: Connect RED probe to anode, BLACK probe to cathode.
3. Note down the deflection of multimeter.
4. Condition 2: Now reverse the connections.
5. Note down the deflection of multimeter again.
6. The result of testing is as follows –
7. If multimeter deflects only in one condition, the diode is OK.
8. If the multimeter deflects in both conditions the diode is FAULTY.
9. If multimeter does not deflect in both conditions, the diode is FAULTY.
10. Refer the diagram for connecting the diode to multimeter.

Observations

Write your observations on a chit of paper. Enlist all the given diodes, with their OK or faulty condition. Attach the chit of observations to your practical booklet.