Forward Bias (I-V) characteristic of PN Junction Diode and Diode as Active Component.
In this video I have explain the Forward bias (I-V) characteristic of Practical PN Junction Diode and Ideal PN Junction Diode. I have also explain why Diode is Active Component and Why Resistor is called as passive component.
We know that in forward bias condition the width of Depletion Layer decreases and In reverse bias condition the width of Depletion layer increases.
The voltage across the conducting PN Junction Diode is always 0.7 volt only.
To study the Forward Bias Characteristic of PN Junction Diode Anode of the Diode should be connected to the Variable Voltage source.
When the variable voltage (VR) is applied at the Anode of Diode starting from 0.1 Volt to 10 volt at that time Diode does not conduct up to 0.6 Volt and the current flowing through the Diode is always Zero up to 0.6 Volt.
But after 0.6 Volt the current starts flowing and it increases as applied voltage increases.
The voltage across the Diode(VD) remains 0.7 volt only for all applied I/P voltages(VR) from 0.7volt to 10 volt which is always shown in IV Characteristics of Diode.
At room temperature (27 degree centigrade) diode conducts from 0.6 volt instead of 0.7 volt because Diode is semiconductor component therefore the conductivity of Diode is increased due to room temperature.
The electrons in Diode are thermally excited at room temperature and current starts flowing at 0.6 volt instead of 0.7 volt.
This forward bias graph is in first quadrant because voltage measured and current flowing through Diode ,both are in positive direction.
The forward resistance of Diode goes on decreasing when applied voltage increases because the Diode is Semiconductor component.
In case of an Ideal Diode, the Diode Current (ID) will start flowing only after 0.7 volt of applied Input Voltage (VR).
The forward resistance of PN Junction Diode decreases as forward applied voltage increases because PN Junction Diode is semiconductor component.
The resistance of all semiconductor devices decreases when, either applied voltage is increased or temperature surrounding to semiconductor devices /component is increased (Negative Temperature Coefficient).
In case of metals the resistance of metal increases when either applied voltage is increased (I.e. when current is excess) or temperature surrounding to metals is increased (Positive Temperature Coefficient).
Why Resistor is called as passive component:
We know the symbol of fixed value resistor with terminal A and B, and its electrical value is fix. Let us consider the resistor of 1KΩ connected to variable voltage source of 1 volt to 10 volt. In this case the current will flow from terminal A to terminal B for all applied voltages from 1 volt to 10 volt.
Now let us reverse the voltage source.
when voltage source is connected in reverse direction to the resistor at that time the current flows in reverse direction from terminal B to terminal A for all applied voltages from 1 volt to 10 volt.
But the value of resistor does not changes for all applied voltages from 1 volt to 10 volt and it remains as 1KΩ only.
Resistor is called as passive component because.
1)The resistor passes current in both direction.
2)The value of resistor does not changes when applied voltages to resistor is changed.
Why PN Junction Diode is called as active component:
PN Junction Diode is called as active component because.
1)PN Junction Diode does not passes current in both direction. It does not conduct in reverse direction,
2)The value of forward resistance of PN Junction Diode changes when applied I/P voltage to PN Junction Diode is changed.
The resistance of PN Junction Diode decreases when applied I/P voltage PN Junction Diode is increased because it is semiconductor component.