Diodes Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. When the diode is zero-biased, what would be the voltage potential across the diode?

1. 1
2. 0
3. -1
4. 2

Ans. The correct answer is b. 0

Explanation: In a zero-biased diode, the potential difference across the diode is zero.

Ques. Which is the ideal example of the bilateral device

1. Transistor
2. Diode
3. Resistor
4. Silicon-controlled rectifier (SCR)

Ans. The correct answer is c. Resistor

Explanation: The resistor is the only bidirectional device listed since it allows current to flow in both directions.

Ques. Diodes transform AC into DC.

1. True
2. False

Ans. The correct answer is a. True

Explanation: Diodes convert alternating current to direct current. Because diodes pass the positive component of the wave while blocking the negative part of the alternating current signal, or if diodes are inverted, they pass just the negative part while blocking the positive part.

Ques. Diodes have _____ terminals.

1. 1
2. 2
3. 3
4. 4

Ans. The correct answer is b. 2

Explanation: Diodes are unilateral two-terminal devices that conduct electricity only in one direction.

Ques. P-N junction diode allows the current to flow in the

1. Forward direction
2. Reverse direction
3. In both forward and reverse directions
4. None of the above

Ans. The correct answer is a. Forward direction

Explanation: The P-N junction diode enables current to flow in the forward direction but prevents it from flowing in the backward direction.

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Short Answers Questions [2 Marks Questions]

Ques. What is a diode?

Ans. An electrical component known as a diode allows current to flow only in one direction. A diode is represented by a triangle symbol by a triangle symbol with a line along one vertex in an electrical circuit diagram.

Ques. What is the dynamic resistance of a diode?

Ans. The dynamic resistance of a diode is defined in terms of the voltage-current ratio, which is the ratio of a small change in voltage to a small change in current, where a changing voltage equals a changing current.

Ques. What is meant by doping?

Ans. In semiconductor technology, doping is the intentional introduction of impurities into intrinsic semiconductors with the aim of changing their optical, structural, and electrical properties.

Ques. What are the main types of diodes?

Ans. The main types of diodes are

• Light-emitting diode
• Avalanche diode
• Laser diode
• Schottky diode
• Photodiode
• P-N junction diode
• Zener diode

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Long Answers Questions [3 Marks Questions]

Ques. What is a Breakdown Diode?

Ans. A diode is referred to as a breakdown diode if it is designed to function at a certain breakdown voltage. 

• The reverse-bias breakdown voltage of a junction can be changed by selecting a different junction doping concentration. 
• The breakdown mechanism for abrupt junctions with excessively strong doping is the Zener effect (tunneling).
• For lightly doped or graded junctions, avalanche (impact ionization) is the most common breakdown. 
• The breakdown voltage remains almost constant as the current changes, and the avalanche breakdown is uniform over the whole junction. 
• Impact ionization plays a role in the breakdown process. 
• The Zener diode is a PN junction diode with a thin junction and strong doping at the same time.

Ques. How is the Zener diode used as a voltage regulator?

Ans. Shunt Voltage Regulators, such as Zener Diodes, are commonly used to regulate voltage across small loads. 

• Zener diodes include a sharp reverse and a stable breakdown voltage over a wide range of currents. 
• As a result, we will connect the zener diode in parallel to the load, causing the applied voltage to reverse bias it. 
• The voltage across the load will be constant if the reverse bias voltage across the Zener diode exceeds the knee voltage.

Ques. What happens when a P-N junction diode is reverse-biased?

Ans. When the positive terminal of the battery is connected to the n-type semiconductor and the negative terminal of the battery is connected to the p-type semiconductor of the diode, then the diode is under a reverse-biased condition. 

• In this biasing the negative terminal of the battery pulls free holes in the p-type while the positive terminal pulls free electrons in the n-type. 
• As a result, the electrons and holes go away from the junction, increasing the depletion width and the potential barrier.

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Very Long Answers Questions [5 Marks Questions]

Ques. What is the working principle of a diode in semiconductors?

Ans. The working of a diode is given below

• The majority of charge carriers in the N-type region are electrons and holes are minority charge carriers. 
• Whereas, in the P-type region, the majority of charge carriers are holes, with electrons being the minority. 
• Because of the concentration difference, the majority charge carriers diffuse and recombine with the minority charge carriers, which are finally concentrated around the junction, forming the Depletion Region. 
• A Reverse Bias situation occurs when the anode or p-type terminal of a diode connects to a negative terminal while the n-type or cathode is connected to the positive terminal of a battery. 
• A Forward Bias condition occurs when the anode or p-type terminal of the diode is connected to a positive terminal and the n-type or cathode is connected to the negative terminal of the battery.

Ques. Explain VI characteristics of the PN junction diode.

Ans. The curve between the voltage and current across the circuit represents the VI characteristics of P-N junction diodes. While current is measured along the y-axis, voltage is measured along the x-axis. The curve enables us to understand that the diode functions in three different zones, which are:

• Zero bias: If there is no external voltage applied then the P-N junction diode is under zero bias condition. The potential barrier at the junction prevents the flow of current.
• Forward bias: When the p-type is connected to the positive terminal and the n-type is connected to the negative terminal then the P-N junction diode is said to be in a forward bias condition. The potential barrier is reduced when the diode is set up in this manner.
• Reverse bias: When the p-type is connected to the negative terminal and the n-type is connected to the positive terminal then the P-N junction diode is said to be in a reverse bias condition. The potential barrier is increased when the diode is set up in this manner.

Ques. List the applications of the diode.

Ans. The following are the applications of the diode

• When reverse-biased, a P-N junction diode can be used as a photodiode since it is light-sensitive.
• It may operate as a solar cell.
• In a clipper, a diode-based circuit is used to clip or cut a piece of either a positive or negative portion of a signal to reshape its waveform.
• The diode can be utilized in LED lighting applications when it is forward-biased.
• It operates as a voltage-controlled oscillator in varactors and as a rectifier in a variety of electric circuits.

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