# PN Junction Diode – Interview Q & A – 1

1. What is depletion region in PN junction ?
The region around the junction from which the mobile charge carriers (electrons and holes) are depleted is called as depletion region. Since this region has immobile ions, which are electrically charged, the depletion region is also known as space charge region.

2. Give the other names of depletion region ?
i. space charge region
ii. Transition region

3. What is barrier potential ?
Because of the oppositely charged ions present on both sides of PN junction an electric potential is established across the junction even without any external voltage source which is termed as barrier potential.

4. What is meant by biasing a PN junction ?
Connecting a PN junction to an external voltage source is biasing a PN junction.

5. What are the types of biasing a PN junction ?
1. Forward bias 2. Reverse bias.

6. What is forward bias and reverse bias in a PN junction ?
When positive terminal of the external supply is connected to P region and negative terminal to N region, the PN junction is said to be forward biased. Under forward biased condition the PN region offers a very low resistance and a large amount of current flows through it.

7. What is reverse bias in a PN junction ?
When positive terminal of the external supply is connected to N type and negative terminal to P type then the PN junction is said to be in reverse bias. Under reverse biased condition the PN region offers a very high resistance and a small amount of current flows through it.

8. What is Reverse saturation current ?
The current due to the  minority carriers in reverse bias is  said to be reverse saturation current. This current is independent of the value of the reverse bias voltage.

9. What is the static resistance of a diode ?
Static resistance R of a diode can be defined as the ratio of voltage V across the diode to the current flowing through the diode.

R = V/ I

Where :
R – Static resistance of a diode
V – Voltage across the diode
I – current across the diode

10. What is the dynamic resistance ?
Dynamic resistance of a diode can be defined as the ratio of change in voltage across the diode to the change in current through the diode.

r = ∆V / ∆I

Where :
r – Dynamic resistance of a diode
∆V – change in voltage across the diode
∆I – change in current through the diode

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