Question

Give reason to explain why n and p regions of a Zener diode are heavily
doped. Find the current through the Zener diode in the circuit given
below : (Zener breakdown voltage is 15 V)
250
20 V
15 V
{1ks x​

Answer 1

Answer:

when external source is connected such that p-region of the diode becomes positive with respect to n-region ,the diode is said to be zener diode are heavily dooed

Answer 2

n and p regions of a Zener diode are heavily  doped:

• Zener diode is a special diode used in zener breakdown region.
• It is connected to work in reverse bias.
• When the current flowing through the normal diode is huge, it breaks the diode.
• Since, the zener diode is highly doped, the depletion region of the zener diode is small, it allows huge current pass through it without any damage.
• But there is breakdown of zener diode when the voltage is more than it can withstand, it is called as zener breakdown voltage and it depends on the doping.

The current through the Zener diode is 5 mA

The image given in the question is attached below.

The current flowing when the resistance is 1 kΩ is:

I₁ = V/R = 15/1000

∴ I₁ = 15 mA

The current flowing when the resistance is 250 Ω is:

I₂ = (20 - 15)/250 = 5/250 = 20/1000

∴ I₂ = 20 mA

Thus, now the current passing through zener diode is:

Iz = 20 mA - 15 mA

∴ Iz = 5 mA