Question

Zener diode is used as (A) Full. wave rectifier (B) amplifier (C) A.C. voltage regulator (D) D.C. voltage regulator

Short answer

The correct application of a Zener diode is as a \( (D) \) D.C. voltage regulator.

Step-by-step solution

Recall the primary function of a Zener diode

A Zener diode is a type of diode designed to work in the breakdown region or reverse-bias. It allows current to flow in the reverse direction when the voltage across its terminals exceeds the Zener voltage. The main function of a Zener diode is to maintain a constant voltage across its terminals.

Analyze each option for the usage of Zener diode

(A) Full wave rectifier - A full wave rectifier is used to convert an alternating (AC) voltage to direct (DC) voltage. A Zener diode is not typically used for this purpose, as it does not offer the necessary rectification properties. (B) Amplifier - An amplifier is a device that increases the amplitude of a signal. A Zener diode is not suitable for this application, as it does not provide amplification. (C) AC voltage regulator - An AC voltage regulator is a device used to maintain a constant output voltage in an AC circuit. While the Zener diode can maintain constant voltage under reverse-bias conditions, it is not designed to regulate AC voltage. (D) DC voltage regulator - A DC voltage regulator is a device used to maintain a constant output voltage in a DC circuit. A Zener diode can be utilized in this application because it maintains a constant breakdown voltage, making it an appropriate device for regulating DC voltage. Based on the analysis above:

Choose the correct application

The correct application of a Zener diode is as a (D) D.C. voltage regulator.

Key concepts

D.C. voltage regulator

A Zener diode serves as an excellent device for working as a D.C. voltage regulator in electronic circuits. Its primary role in this function is to maintain a stable output voltage, even when there are variations in the input voltage or load conditions.

• Stability: By working in the reverse-bias mode, a Zener diode can clamp the voltage at a predetermined level, preventing it from fluctuating. This feature is crucial for sensitive electronic components that require a stable voltage supply.
• Component simplicity: Zener diodes are commonly used due to their straightforward and cost-effective design. They do not require any special additional components to function as a voltage regulator.
• Applications: Zener diodes are widely used in voltage regulation for small power supplies, reference voltages for circuits, and other applications where maintaining a constant voltage is necessary.

In summary, when designing circuits that require consistent voltage levels on the DC side, Zener diodes are the go-to components due to their reliability and simplicity.

Reverse-bias operation

Zener diodes differ from standard diodes in their ability to operate in reverse-bias conditions. The reverse-bias operation is key to their function as voltage regulators.

• Breakdown region: Unlike regular diodes which cease to function effectively when reverse-biased, Zener diodes are intentionally designed to enter a reverse breakdown region. Here, they can conduct current backward while maintaining a constant voltage.
• Zener voltage: Each Zener diode is designed to maintain a specific Zener voltage, which is the point at which the diode breaks down and begins to conduct reverse current. This predetermined voltage is crucial for ensuring voltage regulation.
• Controlled conditions: The reverse-bias operation is controlled, making Zener diodes predictable and reliable in maintaining the desired voltage levels within a circuit.

This reverse-bias operation is fundamental for the Zener diode to perform its voltage regulation task, especially in scenarios where a steady DC voltage supply is crucial.

Constant voltage

The hallmark of a Zener diode is its ability to maintain constant voltage across its terminals. This characteristic is what makes it so valuable in voltage regulation applications.

• Zener effect: The constant voltage attribute is due to the Zener effect, which occurs at the Zener diode's breakdown voltage. When the diode is reverse-biased and the Zener voltage is reached, it creates a constant voltage plateau.
• Voltage clamping: In practice, this means that beyond the Zener voltage, any increase in input voltage does not affect the output voltage, as the excess voltage is absorbed, creating a "clamping" effect.
• Consistency: Whether the input voltage rises above or falls below the set value, the Zener diode adjusts by changing the reverse current flow, keeping the output voltage steady.

Hence, Zener diodes are crucial in circuits where maintaining a consistent voltage is necessary, as they effortlessly handle fluctuations without compromising the load or performance of other components.