What is Electric Diode ? What is a diode with a diagram?

An electric diode is a semiconductor device that allows current to flow in only one direction. It has two terminals:

1. Anode (+) – The positive side
2. Cathode (-) – The negative side

How It Works:

• When the anode is connected to a higher voltage than the cathode (forward bias), current flows.
• When the cathode is at a higher voltage (reverse bias), the diode blocks the current.

Types of Diodes:

• PN Junction Diode – Basic diode used for rectification.
• Light Emitting Diode (LED) – Emits light when current flows.
• Zener Diode – Used for voltage regulation.
• Schottky Diode – Fast switching, low voltage drop.
• Photodiode – Converts light into electrical current.

Diodes are widely used in rectifiers, voltage regulators, signal processing, and LED lighting.

Basic Concept Questions:

1. What is a diode? Explain its working principle with a circuit diagram.
   Answer:
   • A diode is a semiconductor device that allows current to flow in one direction (forward bias) and blocks it in the other (reverse bias).
   • It consists of a PN junction where the P-type semiconductor has holes as majority carriers and the N-type semiconductor has electrons as majority carriers.
   • Working Principle: When forward biased, the depletion region reduces, allowing current flow. In reverse bias, the depletion region widens, preventing current flow.
   Circuit Diagram:
   • Forward Bias: ![Anode(+) →|← Cathode(-)]
   • Reverse Bias: ![Cathode(-) →|← Anode(+)]

2. Define forward bias and reverse bias in a diode.
   Answer:
   • Forward Bias: The P-side of the diode is connected to a higher voltage, and the N-side to a lower voltage, allowing current to flow.
   • Reverse Bias: The P-side is connected to a lower voltage, and the N-side to a higher voltage, preventing current flow.

3. Why does a diode allow current to flow in only one direction?
   Answer:
   • Due to the depletion region and potential barrier, current flows only when the diode is forward biased.
   • In reverse bias, the depletion region widens, blocking current flow.

PN Junction Diode & Characteristics:

4. Draw and explain the V-I characteristics of a PN junction diode.
   Answer:
   • In Forward Bias: The diode starts conducting after the threshold voltage (0.7V for Si, 0.3V for Ge).
   • In Reverse Bias: Very small leakage current flows until breakdown occurs.
   V-I Characteristics Graph:
   • Forward Region: Exponential increase after threshold voltage.
   • Reverse Region: Small leakage current, then sharp increase at breakdown.

5. What is breakdown voltage in a diode? Differentiate between Zener breakdown and Avalanche breakdown.
   Answer:
   • Breakdown Voltage: The voltage at which the diode starts conducting in reverse bias.
   • Zener Breakdown: Occurs in heavily doped diodes at low voltages (< 5V) due to quantum tunneling.
   • Avalanche Breakdown: Occurs in lightly doped diodes at higher voltages (> 5V) due to carrier acceleration and impact ionization.

6. What happens when a diode is connected in reverse bias beyond its breakdown voltage?
   Answer:
   • The diode starts conducting large reverse current, which can damage the diode unless it is a Zener diode designed for breakdown operation.

Types of Diodes & Applications:

7. Explain the working of a Zener diode as a voltage regulator with a circuit diagram.
   Answer:
   • A Zener diode is connected in reverse bias across a load.
   • When the input voltage exceeds the Zener breakdown voltage, the diode maintains a constant output voltage.
   • Used for voltage regulation in power supplies.
   Circuit Diagram:
   • Input → Resistor → Zener Diode (Reverse Bias) → Output

8. What is a Schottky diode? How does it differ from a PN junction diode?
   Answer:
   • A Schottky diode has a metal-semiconductor junction instead of a PN junction.
   • It has faster switching speed and lower forward voltage drop (~0.3V).
   • Used in high-speed circuits and power applications.

9. Explain the principle and working of a photodiode.
   Answer:
   • A photodiode is a light-sensitive diode that generates current when exposed to light.
   • Works in reverse bias, where incoming photons generate electron-hole pairs, increasing current flow.
   • Used in light sensors, cameras, and optical communication.

10. Why do LEDs emit light while ordinary diodes do not?
    Answer:

• In LEDs, when electrons recombine with holes, they release energy in the form of visible light (electroluminescence).
• In ordinary diodes, energy is released as heat instead of light.

Practical & Numerical Questions:

11. A silicon diode has a forward voltage drop of 0.7V. If a current of 10mA flows through it, what is the power dissipated?
    Answer:

• Power = Voltage × Current
• P=0.7V×10mA=0.007W=7mWP = 0.7V \times 10mA = 0.007W = 7mWP=0.7V×10mA=0.007W=7mW

12. A full-wave rectifier uses two diodes. If the input AC voltage is 10V RMS, what will be the approximate DC output voltage?
    Answer:

• VDC_{DC}DC​ = 0.9 × Vrms_{rms}rms​
• VDC=0.9×10V=9VV_{DC} = 0.9 \times 10V = 9VVDC​=0.9×10V=9V

13. A Zener diode with a breakdown voltage of 6V is used in a regulator circuit. What will be the output voltage if the input is 12V?
    Answer:

• The Zener diode maintains constant voltage at 6V.
• Output Voltage = 6V (same as Zener breakdown voltage).

These answers cover both theoretical and numerical aspects of Electric Diodes, useful for board exams, engineering entrances (JEE, GATE), and university exams. Let me know if you need more clarification! 😊