Question

In forward bias made, the PN junction diode resistance will (A) infinity (B) zero (C) less (D) more

Short answer

In forward bias mode, a PN junction diode allows the current to flow through it with minimal resistance. While the resistance is not zero, it is less than the resistance in reverse bias mode. Therefore, the correct answer is (C) less.

Step-by-step solution

Understanding PN Junction Diode in Forward Bias Mode

A PN junction diode is made up of two semiconductor materials, P-type and N-type. In a forward bias mode, the P-side of the diode is connected to the positive terminal of the battery, and the N-side is connected to the negative terminal. This connection allows the electrons in the N-side to flow towards the P-side, which results in current flow through the diode.

Resistance in Forward Bias Mode

In forward bias mode, the diode allows the current to flow through it with minimal resistance. The resistance is not zero, as there is still some opposition to the flow of current due to the depletion region, but it is less than the resistance in reverse bias mode, where the diode does not allow the current to flow through it.

Choosing the Correct Option

Based on the understanding of PN junction diode in forward bias mode and its resistance, we can choose the correct option among the given ones: (A) infinity - Incorrect, as the resistance is not infinitely high in forward bias mode. (B) zero - Incorrect, as there is still some opposition to the flow of current, even if minimal. (C) less - Correct, as the resistance in forward bias mode is less than in reverse bias mode. (D) more - Incorrect, as the resistance is not higher in forward bias mode compared to reverse bias mode. So, the correct answer is (C) less.

Key concepts

Understanding Forward Bias

When discussing PN junction diodes, forward bias is an essential concept. A diode in forward bias mode means the P-side of the diode is connected to the positive terminal of a power source, while the N-side is attached to the negative terminal. This setup facilitates the movement of charge carriers: electrons move from the N-side towards the P-side. As a result, the depletion region at the junction becomes narrow, allowing current to flow more freely through the diode.
Forward bias is crucial for the functioning of diodes. It permits a current flow that is critical in various electronic applications, such as rectifiers and switches.

Resistance in PN Junction Diodes

In a forward-biased PN junction diode, resistance plays a key role in its operation. Even though the diode allows for current flow, there is still some level of resistance encountered. This resistance is much lower than in the reverse-biased condition, in which the diode blocks current.

• The depletion region shrinkage accounts for this low resistance in forward bias.
• The conduction of charge carriers across the junction faces minimal opposition.

It's important to note that the resistance is not zero, as the junction will always present a minimal opposing force to current flow. Thus, in forward bias, we describe the diode resistance as 'less.'

Current Flow Through the Diode

Current flow in a forward-biased diode is largely unrestricted because of the reduced barrier at the PN junction. When electrons from the N-type material migrate towards the P-type, they fill electron holes, resulting in a smooth current flow from one side to the other.

• This flow is indicative of a low-energy barrier due to decreased junction resistance.
• Current flow is also assisted by the applied voltage, which motivates the charge carriers to cross the junction.

This efficient current flow is integral in achieving the desired functionality in circuits that utilize diodes, such as converting AC to DC power.

Role of Semiconductor Materials

The foundational elements of a PN junction diode are the semiconductor materials: P-type and N-type. These semiconductors are doped to create charge carriers.

• P-type semiconductors have an abundance of holes (positive charge carriers).
• N-type semiconductors contain an excess of electrons (negative charge carriers).

The interaction between these two types of materials at the junction is what allows for the unique properties of the diode. When forward-biased, these semiconductors enable efficient current flow by overcoming the initial depletion barrier. Understanding these materials is key to grasping why and how diodes operate in different biasing states.