1. What are semiconductors?
Answer: Semiconductors are materials with electrical conductivity between that of conductors and insulators. They can conduct electricity under certain conditions, making them essential for electronic devices.
2. Describe the I-V characteristics of a semiconductor diode in forward bias.
Answer: In forward bias, the diode conducts electricity once the applied voltage exceeds the threshold voltage (typically 0.7V for silicon diodes). The current increases exponentially with the applied voltage.
3. Describe the I-V characteristics of a semiconductor diode in reverse bias.
Answer: In reverse bias, the diode blocks current flow until the breakdown voltage is reached, at which point a small leakage current flows. Beyond this breakdown voltage, a significant current can flow, potentially damaging the diode.
4. How does a diode function as a rectifier?
Answer: A diode allows current to pass in one direction (forward bias) and blocks it in the reverse direction. This property is used to convert alternating current (AC) to direct current (DC) in rectifier circuits.
5. Explain the I-V characteristics of a Light Emitting Diode (LED).
Answer: An LED emits light when forward biased. The I-V curve shows a threshold voltage above which current increases rapidly and light is emitted. The reverse bias I-V characteristics are similar to a standard diode, blocking current flow.
6. What is a photodiode and its I-V characteristics?
Answer: A photodiode is a semiconductor device that converts light into electrical current. In reverse bias, the current increases with light intensity, exhibiting low current in darkness and higher current under illumination.
7. Describe the working principle of a solar cell.
Answer: A solar cell converts light energy directly into electrical energy through the photovoltaic effect. When light photons strike the cell, they generate electron-hole pairs, creating a current as these charge carriers move across the junction.
8. Explain the I-V characteristics of a Zener diode.
Answer: A Zener diode conducts in reverse bias once the reverse breakdown voltage is reached, allowing a stable current to flow. In forward bias, it behaves like a regular diode with an exponential increase in current.
9. How is a Zener diode used as a voltage regulator?
Answer: A Zener diode maintains a constant output voltage despite changes in the input voltage or load conditions by operating in its reverse breakdown region, stabilizing the voltage across its terminals.
10. What is the function of an OR gate in digital circuits?
Answer: An OR gate outputs a high (1) signal if any of its inputs are high. It implements logical addition.
11. Describe the function of an AND gate.
Answer: An AND gate outputs a high (1) signal only if all of its inputs are high. It implements logical multiplication.
12. What does a NOT gate do?
Answer: A NOT gate, also known as an inverter, outputs the opposite of the input signal. If the input is high (1), the output is low (0), and vice versa.
13. How does a NAND gate function?
Answer: A NAND gate outputs a low (0) signal only if all its inputs are high. It is the inverse of an AND gate.
14. What is the purpose of a NOR gate?
Answer: A NOR gate outputs a low (0) signal if any of its inputs are high. It is the inverse of an OR gate.
15. Compare the I-V characteristics of a regular diode and a Zener diode.
Answer: A regular diode conducts in forward bias with an exponential I-V curve and blocks reverse current until breakdown. A Zener diode also conducts in forward bias but allows reverse current flow at its breakdown voltage, maintaining a stable voltage.
16. What is the significance of the threshold voltage in a diode’s I-V characteristics?
Answer: The threshold voltage is the minimum forward bias voltage required for a diode to conduct significantly. Below this voltage, the current is minimal.
17. Describe the photovoltaic effect in a solar cell.
Answer: The photovoltaic effect is the generation of voltage and current in a material upon exposure to light. In a solar cell, photons excite electrons, creating electron-hole pairs and generating electricity.
18. Explain the role of doping in semiconductors.
Answer: Doping involves adding impurities to a semiconductor to change its electrical properties. N-type doping adds electrons, while P-type doping creates holes, enhancing conductivity.
19. How do LEDs differ from regular diodes?
Answer: LEDs emit light when forward biased, converting electrical energy into light energy. Regular diodes do not emit light and are primarily used for rectification.
20. What is the purpose of using logic gates in digital circuits?
Answer: Logic gates are used to perform basic logical functions on binary inputs, forming the building blocks of digital circuits. They are essential for designing complex digital systems like computers and communication devices.