Explain construction, features and applications of Zener diode.

Construction of Zener Diode:

A Zener diode is a heavily doped PN junction diode that exhibits a sharp reverse breakdown voltage. It is constructed by heavily doping both the P and N regions of a semiconductor material, typically silicon. The heavy doping results in a narrow depletion region and a high electric field across the junction.

Features of Zener Diode:

1. Sharp Reverse Breakdown Voltage: Zener diodes have a sharp reverse breakdown voltage, also known as the Zener voltage (V_Z). When the reverse voltage reaches the Zener voltage, the diode breaks down and allows a large reverse current to flow. The Zener voltage is typically in the range of 2.4 volts to 200 volts.

2. Constant Voltage Regulation: In the breakdown region, the Zener diode exhibits a constant voltage drop across its terminals. This property makes it very useful as a voltage regulator. When the reverse voltage exceeds the Zener voltage, the Zener diode starts conducting heavily, and the voltage across it remains relatively constant, even if the reverse current increases.

3. Low Dynamic Resistance: Zener diodes have a very low dynamic resistance in the breakdown region. This means that the Zener diode can provide a stable reference voltage with a very small change in current. The dynamic resistance is typically in the range of a few ohms.

4. High Power Dissipation: Zener diodes are capable of dissipating a significant amount of power without being damaged. This makes them suitable for use in applications where high power is involved.

Applications of Zener Diode:

1. Voltage Regulation: Zener diodes are primarily used as voltage regulators. They can provide a stable reference voltage for various electronic circuits. They are commonly used in power supplies, amplifiers, and other electronic devices to regulate the voltage.

2. Clipping and Clamping: Zener diodes can be used for clipping and clamping circuits. In clipping circuits, they prevent the output voltage from exceeding a certain level. In clamping circuits, they limit the output voltage to a specific range.

3. Overvoltage Protection: Zener diodes can be used to protect sensitive electronic circuits from overvoltage conditions. They can divert excess voltage away from the circuit and prevent damage to the components.

4. Voltage Reference: Zener diodes are often used as voltage references in various electronic circuits. They provide a stable and precise voltage reference for other components in the circuit.

5. Signal Limiting: Zener diodes can be used to limit the amplitude of a signal. They can prevent the signal from exceeding a certain threshold voltage, thus protecting downstream components from damage.

6. High-power rectifiers: Zener diodes can be used as high-power rectifiers by operating them in the avalanche breakdown region. In this region, they exhibit a very low forward voltage drop and can handle high currents.