As an expert in the field of electronics, I'd like to clarify that the primary function of a Zener diode is to maintain a stable voltage level across its terminals when it is in reverse bias. However, the question at hand is whether a Zener diode can be used in forward bias, and the answer is yes, but with certain considerations.

In the forward bias condition, a Zener diode behaves similarly to a standard signal diode. It allows current to flow in the forward direction once the voltage across it reaches the diode's forward voltage threshold, typically around 0.7 volts for silicon diodes. The diode then operates in its linear region, where the voltage across the diode increases only slightly with an increase in the forward current. This behavior is quite useful for general purpose applications where the diode is used as a rectifier or in signal processing circuits.

However, the unique feature of a Zener diode becomes apparent when it is in reverse bias. Under reverse bias, up to a certain limit, the Zener diode exhibits a high resistance to the flow of current. This limit is known as the breakdown voltage, which is the voltage at which the Zener diode is specifically designed to operate in its reverse-biased mode. Beyond this voltage, the diode enters the Avalanche Breakdown region, where it allows a large current to flow, while maintaining a nearly constant voltage across its terminals. This characteristic is what makes Zener diodes ideal for voltage regulation applications.

The reference to the Zener diode being used in its "reverse bias" is correct in the context of its primary application for voltage regulation. However, it is important to note that the diode can indeed operate in forward bias, but it does not offer the unique voltage stabilization properties that it provides in reverse bias.

In summary, while a Zener diode can be used in forward bias like any other diode, its special characteristics that make it valuable in circuit design are realized when it is reverse biased and operating in the Zener region, providing a stable reference voltage.

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When biased in the forward direction it behaves just like a normal signal diode, but when a reverse voltage is applied to it, the voltage remains constant for a wide range of currents. Avalanche Breakdown: There is a limit for the reverse voltage. ... The Zener Diode is used in its "reverse bias".read more >>