Question

The load voltage is approximately constant when a zener diode is (A) Forward biased (B) Reverse biased (C) Operating in breakdown region (D) Unbiased

Short answer

The load voltage is approximately constant when a Zener diode is operating in the breakdown region (Choice C). This is because in this state, the Zener diode regulates the voltage across it by allowing excess current to flow in the reverse direction, thereby maintaining the voltage across its terminals nearly constant.

Step-by-step solution

Understand Zener Diode Characteristics

A Zener diode is a type of diode designed to allow the flow of current in the reverse direction when a certain reverse-biased voltage (called the Zener voltage) is reached. It is used for voltage regulation in electronic circuits, maintaining a constant voltage across its terminals even with changes in current.

Forward biased Zener Diode

When a Zener diode is forward biased (Choice A), it behaves like a regular diode, allowing current to flow in the forward direction. However, it does not maintain a constant load voltage in this condition because it does not utilize the Zener breakdown effect, which is the characteristic responsible for voltage regulation.

Reverse biased Zener Diode

When a Zener diode is reverse biased (Choice B), it blocks current flow in the reverse direction until the applied reverse voltage reaches the Zener voltage (the breakdown voltage). At this point, the Zener diode conducts in the reverse direction, but it does not maintain a constant load voltage since the Zener breakdown effect is not utilized in this condition.

Zener Diode Operating in Breakdown Region

When a Zener diode is operating in the breakdown region (Choice C), it maintains a constant voltage across its terminals, known as the Zener voltage. This is the desired condition for maintaining constant load voltage. In this region, the Zener diode regulates the voltage across it by allowing excess current to flow in the reverse direction and keeping the voltage across its terminals nearly constant.

Unbiased Zener Diode

When a Zener diode is unbiased (Choice D), neither forward nor reverse voltage is applied across its terminals. In this condition, the diode does not conduct current and does not maintain a constant load voltage. #Conclusion# Among the given options, the load voltage remains approximately constant when a Zener diode is \(operating\) \(in\) \(breakdown\) \(region\) (Choice C).