Explore the key concepts of Zener diode breakdown mechanisms and voltage regulation with this quiz designed for students and electronics enthusiasts. Gain a deeper understanding of how Zener diodes operate in various circuits, focusing on their breakdown behaviors and regulation roles.
What physical process primarily causes Zener breakdown in a heavily-doped Zener diode operating below 5V?
Explanation: Zener breakdown occurs mainly due to quantum tunneling of electrons across a very narrow, heavily-doped p-n junction when the reverse voltage exceeds a critical value. Thermal runaway refers to a dangerous overheating process, not a controlled breakdown. Junction heating is a general effect and not the specific cause of Zener breakdown. Avalanche multiplication describes a different breakdown mechanism that dominates at higher reverse voltages, typically above 6V.
How does a Zener diode regulate voltage across a load in a simple shunt regulator circuit?
Explanation: A Zener diode in reverse bias regulates voltage by maintaining a nearly constant voltage (its breakdown voltage) across the load, despite changes in input supply or load resistance. Increasing current flow through the load or reducing circuit resistance is not the function of the Zener diode itself. While some power is dissipated as heat, the diode does not dissipate all input power; most energy is still provided to the load.
In Zener diodes with breakdown voltages above approximately 6V, which mechanism mainly controls the breakdown process?
Explanation: For Zener diodes with breakdown voltages above 6V, avalanche multiplication dominates, where carriers gain enough energy to knock loose more carriers, leading to a large increase in current. Quantum resonance and tunnel effect (tunneling) are more associated with lower-voltage breakdowns. Capacitive discharge is unrelated to the breakdown mechanism and involves energy release from a capacitor.
Which orientation must a Zener diode have in a voltage regulator so it operates in its breakdown region?
Explanation: The Zener diode must be reverse biased to operate in its breakdown region, commonly placed across the power supply and load in parallel (shunt configuration). Forward biasing does not utilize the Zener breakdown effect; instead, the diode would behave like a regular diode in that orientation. Placing the diode in series, either forward or reverse, is not standard for voltage regulation using Zener breakdown.
If the load resistance in a Zener shunt voltage regulator decreases while input voltage remains constant, what is likely to happen?
Explanation: When load resistance decreases, more current is drawn by the load, which reduces the current flowing through the Zener diode (since total current is shared between the load and the diode). The voltage across the Zener diode remains almost unchanged if it's in breakdown. The Zener diode does not switch to forward bias under these conditions. The idea that current through the Zener increases is incorrect—it actually decreases as more current favors the load.