NEIEP Mechanics Practice Exam

What are Zener diodes designed to do?

1. Operate in series mode

2. Operate in forward bias mode

3. Operate in reverse bias mode

4. Operate in parallel mode

The correct answer is: Operate in reverse bias mode

Zener diodes are specifically designed to operate in reverse bias mode. When connected in reverse bias, a Zener diode allows current to flow once the voltage across it reaches a certain predefined level, known as the Zener breakdown voltage. This characteristic makes Zener diodes highly effective for voltage regulation purposes, as they can maintain a constant output voltage even when the input voltage fluctuates. In reverse bias mode, the Zener diode remains in a non-conducting state until the applied reverse voltage reaches the breakdown threshold. Once this occurs, the diode conducts current while maintaining this stable voltage across its terminals, providing a reliable reference voltage in various electronic circuits. Other methods of operation such as series mode, forward bias mode, and parallel mode do not accurately characterize the function of Zener diodes. In forward bias, standard diodes would conduct current normally, but this is not the primary operation for Zener diodes. Series mode and parallel mode are more relevant to configuration in circuits rather than specific functionalities of the Zener diode itself.