Question

Is Zener voltage positive or negative?

Answer 1

The **Zener voltage** refers to the voltage at which a **Zener diode** starts to conduct in reverse bias, maintaining a stable voltage across it despite changes in the reverse current. This voltage is typically referred to as the **Zener breakdown voltage** or **Zener knee voltage**.

The **polarity** of the Zener voltage depends on the orientation of the Zener diode in the circuit:

- When the **Zener diode is reverse biased**, the voltage is **negative** across the diode if the anode is connected to the negative terminal and the cathode is connected to the positive terminal. In this configuration, the diode does not conduct until the reverse voltage exceeds the Zener breakdown voltage (often referred to as the Zener voltage), after which it starts to conduct in reverse and maintains a stable voltage (Zener voltage).
  
- If the Zener diode is **forward biased**, it behaves like a normal diode and conducts when the voltage exceeds about 0.7V (for silicon diodes). This is not the Zener voltage, but rather the **forward voltage**.

### Key Points:
1. **Zener voltage** refers to the breakdown voltage in reverse bias, and it is generally a **negative voltage**.
2. The diode only starts to conduct in reverse bias when the reverse voltage exceeds the Zener voltage (negative voltage in reverse bias).
3. The value of the Zener voltage (e.g., -5V, -12V) will be negative since it is specified for the reverse bias direction.

So, to directly answer your question, **Zener voltage is negative** in reverse bias conditions.