In this video, the avalanche breakdown and Zener breakdown effects in the PN junction diode have been explained.
By watching this video, you will learn the following topics:
0:15 Avalanche breakdown effect
4:18 Zener diode and Zener breakdown effect
7:41 Effect of temperature of Avalanche and Zener breakdown voltages
The Avalanche breakdown effect:
In the reverse bias condition, when the applied voltage across the PN junction diode, is more than the breakdown voltage (Vb) then suddenly a reverse saturation current shoots up.
Because at the applied breakdown voltage the electric field in the depletion region will be much stronger. And due to this electric field, the minority charge carriers will get accelerated. And due to enough kinetic energy, when they collide with the silicon atoms in the crystal, they can knock out the bound electrons of the atom. Under the influence of electric field, the knocked out electrons (along with the previously accelerated electrons which have knocked out them) will again collide with the other silicon atoms and will knock out the bound electrons.
So, in this way, due to this impact ionization, a lot of minority charge carriers are generated in the depletion region. And due to that, the minority current will increase drastically. So, this effect is known as the avalanche breakdown effect and the voltage at which it occurs in know as the breakdown voltage. The Avalanche breakdown effect is seen in the lightly doped didoes.
Zener Breakdown effect:
The Zener effect is usually seen in the heavily doped diodes. (e.g Zener diodes)
In heavily doped diodes the depletion region is much narrower than the normal diodes. So, in reverse bias condition, at a specific voltage, the electric field in the depletion region will be so strong that, the strong electric field can knock out the bound electrons of the silicon atom. And due to that, the electron-hole pair is created in the depletion region. And these due to this additional minority carriers there is a sudden rise in the reverse saturation current.
This effect is known as the Zener breakdown effect.
And the voltage at which this effect occurs is known as the Zener voltage.
The Zener effect occurs at the lower voltage than the avalanche effect. And in the Zener diodes, depending on the breakdown voltage, both effects are visible.
For the Zener diodes, whose breakdown voltage is in the range of 4-5 V, the Zener effect is predominant.
While for the breakdown voltages, beyond 6V, the avalanche effect is predominant.
Effect of temperature on Zener and avalanche breakdown voltages:
As temperature increases, the Zener breakdown voltage reduces.
While with temperature, the avalanche breakdown voltage increases.
This video will be helpful to all students of science and engineering in understanding the avalanche and Zener breakdown effect in PN junction diode.
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5 июл 2024
