PN Junction Diode Characteristics[ V-I Forward and Reverse]

PN Junction diode is a semiconductor devices which conducts from only one side. Hence it is an unidirectional device. As the name stands PN junction Diode is made up of P type and N Type semiconductor material. It is used majorly in rectifier and voltage regulator circuits. PN Junction diode characteristics provide us the information about the habitual working of the diode. V-I Characteristics stands for voltage and current. Here, the characteristics is the graph where the voltage is plotted on the X-Axis and the Current on the Y-Axis. The majorly used diodes are 1N4007 series. They are widely used in rectifier circuits.

There are two modes of Operation. Forward Bias and Reverse Bias.

  •  In Forward Bias the voltage source is connected in forward bias. It means the positive terminal is connected to the anode of the diode and the negative terminal of the battery is connected to the cathode of the anode.
  • In Reverse Bias, the positive terminal of the voltage source is connected to the cathode of the diode and the negative terminal of the source is connected to the anode of the diode.
  • We will learn and study the characteristics of the both the bias techniques

Circuit Diagram of PN Junction Diode Characteristics:

  • Forward Bias

PN Junction Diode Characteristics Circuit Diagram- Forward Bias
PN Junction Diode Characteristics Circuit Diagram- Forward Bias

The above circuit can be simulated using Multisim Software.

A voltage source and resistor and diode are connected in series. The above configuration is a foraward bias as the positive terminal of the DC Source is connected to the anode and negative terminal is connected to the cathode.

  • When the input voltage to the diode is less than around 0.7 V no current flows in the diode.
  • There is a depletion region present between the P and N type materials which disallows the flow of electrons.
  • As the input voltage rises more than 0.7 the N type electrons are attracted towards the P -type material and the photons from P-Type are attracted towards the N-Type material.
  • Hence the current starts flowing. As we increase more input voltage more current will flow. The input voltage must be limited to the maximum value.
  • Check out the diode specifications in the datasheets before using it.

In our circuit we are using diode 1N4001G. Checkout the Datasheet.

Forward Bias output:

 

PN Junction Diode Charcacteristics of Forward Bias
PN Junction Diode Charcacteristics of Forward Bias
  • Reverse Bias

PN Junction Diode Characteristics- Reverse Bias
PN Junction Diode Characteristics- Reverse Bias

In reverse bias- Note the battery connection. It has been reversed. Therefore the negative terminal is connected to the anode of the diode and the positive terminal of the voltage source is connected to the cathode. As the reverse input voltage increases the electrons from N-Type are attracted towards positive terminal away from the junction.

Similarly, the P-Type photons are attracted towards the Negative terminal of the voltage source away from the junction. Therefore there is no junction crossing and the depletion layer near the junction tends to increase. Therefore there is no current flowing through the diode.

PN Junction Diode Characteristics Output- Reverse Bias
PN Junction Diode Characteristics Output- Reverse Bias

As you can see from the above image there is no current flowing through the diode. The above image is a characteristics of the 1N4001 Diode. It can block maximum up to 50 V in reverse bias. Therefore, when we increase the input reverse voltage above 50 V breakdown occurs and large current starts flowing. This situation should be avoided as diode get burned out.

Check out our video for the simulation:

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