A diode (PN junction) when reverse biased act as

by

Electrical Engineering XYZ MCQs

A diode (PN junction) when reverse biased act as:

  1. Capacitor
  2. On Switch
  3. Off Switch
  4. Zener diode

Correct answer: 3. Off Switch

Explanation:

A diode acts as an off switch when it is reverse biased.
A diode is a semiconductor device that allows current to flow in one direction while blocking it in the opposite direction. Forward bias and reverse bias are two states in which a diode can be operated, and they have distinct characteristics:

  1. Forward Bias:
    • In forward bias, the positive terminal of the voltage source is connected to the P-type semiconductor (anode), and the negative terminal is connected to the N-type semiconductor (cathode) of the diode.
    • This configuration reduces the width of the depletion region at the junction between the P and N-type materials, allowing majority charge carriers (electrons in the N-type material and holes in the P-type material) to flow across the junction, thereby enabling current to flow through the diode.
    • Forward bias typically requires a voltage above the diode’s forward voltage drop (typically around 0.6 to 0.7 volts for silicon diodes) to overcome the built-in potential barrier at the junction.
  2. Reverse Bias:
    • In reverse bias, the polarity of the voltage source is reversed, with the positive terminal connected to the N-type semiconductor (anode) and the negative terminal connected to the P-type semiconductor (cathode).
    • This configuration increases the width of the depletion region at the junction, preventing significant current flow through the diode.
    • While a small leakage current may flow due to minority carriers, it is typically very low (in the range of nanoamperes to picoamperes) compared to the current in forward bias.
    • Reverse bias is often used to block current flow in one direction, allowing the diode to act as a switch or a rectifier in electronic circuits.

In summary, forward bias allows current to flow through the diode, while reverse bias blocks current flow, exploiting the properties of the P-N junction within the diode structure.

Leave a Reply