Diode Interview Questions and Answers

This questionnaire will help you prepare for job interviews for various diode skill-based positions, as well as be useful during vivas for engineering students.

Diode Questions and Answers

Question 1: What is a diode, and how does it work?

Answer: A diode is a semiconductor device that allows current to flow in one direction only. It has two terminals: an anode and a cathode. When the anode is positive with respect to the cathode, the diode is forward-biased and allows current to flow. When the anode is negative relative to the cathode, the diode is reverse-biased, and it blocks current.

Question 2: Explain the concept of forward bias and reverse bias in a diode.

Answer: In forward bias, the positive terminal of the power supply is connected to the anode and the negative terminal to the cathode, which reduces the potential barrier and allows current to flow through the diode. In reverse bias, the connections are reversed, which increases the potential barrier and prevents current from flowing.

Question 3: What is the purpose of the depletion region in a diode?

Answer: The depletion region is the area around the p-n junction where mobile charge carriers are depleted, creating an electric field that opposes further movement of charge carriers. This region is crucial for the diode’s rectifying behavior, as it forms the potential barrier that must be overcome for current to flow in the forward direction.

Question 4: What is the breakdown voltage in a diode?

Answer: The breakdown voltage is the minimum reverse voltage at which a diode begins to conduct in reverse. This occurs when the reverse bias voltage is so high that it causes a significant increase in current, which can lead to diode damage if not controlled. Zener diodes are designed to operate safely in breakdown regions.

Question 5: Differentiate between a Zener diode and a regular diode.

Answer: A regular diode allows current to flow only in one direction (forward bias) and blocks it in reverse bias. A Zener diode, however, is designed to conduct in reverse bias when the reverse voltage exceeds a certain value, known as the Zener breakdown voltage. Zener diodes are commonly used for voltage regulation.

Question 6: What is the ideal diode equation?

Answer: The ideal diode equation is as follows:

$I = I_s \cdot (e^{\frac{V}{n \cdot V_t}} - 1)$

Where:

• $I$ = Diode current
• $I_s$ = Saturation current
• $V$ = Voltage across the diode
• $n$ = Ideality factor
• $V_t$ = Thermal Voltage

Question 7: Explain the concept of a Schottky diode and its advantages.

Answer: A Schottky diode is a type of diode with a metal-semiconductor junction rather than a p-n junction. It has a lower forward voltage drop (typically 0.2 to 0.3 V) and faster switching speeds compared to regular diodes. These characteristics make it ideal for high-frequency and high-speed applications.

Question 8: What is the difference between a light-emitting diode (LED) and a regular diode?

Answer: An LED is a type of diode that emits light when current flows through it in the forward direction. Unlike regular diodes, which are used for rectification, LEDs are used as light sources in various applications, such as displays, indicators, and lighting.

Question 9: What is reverse recovery time in a diode?

Answer: Reverse recovery time is the time it takes for a diode to switch from the conducting (forward-biased) state to the non-conducting (reverse-biased) state. It is the duration during which a diode allows reverse current to flow after switching. This parameter is important in high-speed switching applications.

Question 10: Why is a diode used in rectification circuits?

Answer: Diodes are used in rectification circuits because they allow current to flow in only one direction, converting alternating current (AC) to direct current (DC). In a rectifier circuit, diodes block the negative half-cycles of AC, allowing only the positive half-cycles to pass, thus creating a pulsating DC output.