Zener Diode Characteristics
Explore the **I-V characteristics** of a **Zener Diode**, particularly its ability to maintain a constant **Breakdown Voltage ($V_z$)** when heavily reverse-biased. This property makes it ideal for **voltage regulation**.
Help & Instructions
▼- **Set $V_z$:** Choose a specific Zener Breakdown Voltage ($V_z$) using the slider.
- **Adjust Voltage ($\mathbf{V}$):** Use the main voltage slider to sweep from Forward Bias ($\approx +1 \text{ V}$) into deep Reverse Bias ($\approx -15 \text{ V}$).
- **Observe Stabilization:** Note how the voltage across the diode remains close to $V_z$ even as the negative current ($I_z$) increases rapidly after breakdown.
- Identify the **Zener Knee Current** ($I_{zk}$) and **Breakdown Voltage** ($V_z$).
- Understand the diode's function as a **voltage regulator** in the breakdown region.
- Differentiate Zener characteristics from a normal P-N diode.
Experiment: Measuring Zener Current ($I_z$)
Zener operation is defined by the steep slope at $V \approx -V_z$.
Regulation Condition:
Zener Diode regulates when reverse voltage is $\leq V_z$ and current is $\geq I_{zk}$.
Current at 0.00 V: $I \approx 0 \text{ mA}$
The Zener Diode is engineered to operate reliably in the **reverse breakdown** region. Unlike a standard diode, its **heavy doping** causes the depletion region to be thin, allowing a massive reverse current to flow at a precise, low voltage ($V_z$) without permanent damage.
Detailed Physics Explanation
When the reverse voltage reaches $V_z$, the electric field across the thin depletion region becomes extremely strong. This field directly rips electrons from their covalent bonds, leading to a sudden, large increase in reverse current. This effect is used to **clamp** the voltage at $V_z$.
In the breakdown region, the Zener curve is nearly vertical, meaning large changes in current ($\Delta I_z$) result in only tiny changes in voltage ($\Delta V_z$). The ratio $\frac{\Delta V_z}{\Delta I_z}$ defines the **Zener Impedance ($Z_z$)**, which is intentionally very low for good regulation.
