11.4 : ツェナーダイオード

Like regular diodes, a Zener diode allows current to flow in forward-bias and blocks current in reverse bias.

However, if the reverse bias voltage exceeds the Zener diode's reverse breakdown voltage, current will flow through it. The typical breakdown voltage for a Zener diode can range from a few volts to several hundred volts.

In reverse bias operation, particularly beyond the knee current, the Zener diode exhibits almost vertical I-V behavior.

As the source voltage increases, more current flows through the Zener diode, but the voltage across it remains constant.

The slope of the I-V characteristics in reverse bias is defined as the reciprocal of the incremental resistance of the Zener diode.

As the current through the Zener diode deviates from its specified value, the voltage across the Zener varies only slightly. So, Zener diodes are used as voltage regulators in sensitive electronics.

However, this voltage deviation becomes more pronounced when the current through the zener nears the knee current, making the Zener diode suitable as a voltage regulator primarily in high-current regions.