Semiconductor Diode MCQ Questions & Answers | Electrical Engineering

In semiconductor diodes, the biasing conditions determine the direction of current flow. Let's analyze the options:

Option A: Forward
- When the crystal current (diode current) is large, it typically indicates that the diode is under forward bias. In forward bias, the voltage applied to the diode allows a significant current to flow through it.

Option B: Inverse
- When the diode is under reverse bias, the crystal current should be very low or negligible. Reverse bias means that the voltage applied to the diode is in the opposite direction of its normal operation, and it prevents significant current flow.

Option C: Poor
- The term "poor" is not commonly used to describe the biasing condition of a diode. It doesn't convey a specific biasing state.

Option D: Reverse
- While a reverse bias condition does restrict current flow in a diode, it is not the condition associated with a large crystal current (diode current).

Therefore, the correct answer is Option A: Forward. When the crystal current (diode current) is large, the diode is typically under forward bias, allowing a significant current to flow through it.

A Zener diode is specifically designed to operate in the reverse breakdown region, known as the Zener breakdown region.

Voltage Regulator: Zener diodes are commonly used as voltage regulators. They maintain a constant output voltage despite variations in the input voltage or load conditions. This is achieved by exploiting their ability to stabilize the voltage across their terminals when operating in the breakdown region.

Amplifier: Zener diodes are not used as amplifiers; their primary function is voltage regulation.

Rectifier: While Zener diodes can be used in rectifier circuits, their primary application is for voltage regulation rather than rectification.

Multivibrator: Zener diodes are not used as multivibrators. Multivibrators are circuits used for generating square waves and timing applications, typically involving transistors or other components.

Thus, Option B: a voltage regulator is the correct answer.