Construction of a Transistor

The construction of a transistor involves three regions: the emitter, the base, and the collector. Each region is made of a specific type of semiconductor material, either p-type or n-type. The arrangement of these regions determines the functionality and characteristics of the transistor.

Emitter, Base, and Collector Regions

1. Emitter: The emitter region is heavily doped with impurities to enhance its conductivity. It is typically made of n-type material. The emitter supplies majority charge carriers (electrons in an NPN transistor) to the base region.

2. Base: The base region is lightly doped and thinner compared to the emitter and collector regions. It is made of either p-type or n-type material, depending on whether the transistor is NPN or PNP. The base controls the flow of charge carriers from the emitter to the collector.

3. Collector: The collector region is lightly doped but larger in size compared to the emitter region. It is typically made of p-type material in an NPN transistor. The collector collects the majority charge carriers (electrons in an NPN transistor) from the base region.

True Statement

The true statement in the construction of a transistor is:

c) The collector is made physically larger than the emitter region.

Explanation:

The collector is made physically larger than the emitter region for several reasons:

1. Power Dissipation: The collector dissipates more power compared to the emitter. By making the collector physically larger, it can handle higher power dissipation without causing overheating or damage to the transistor.

2. Charge Collection: The collector region is responsible for collecting the majority charge carriers (electrons in an NPN transistor) from the base region. By making the collector larger, it increases the surface area available for charge collection, improving the transistor's efficiency and performance.

3. Reverse Bias: In normal operation, the emitter-base junction is forward-biased, while the collector-base junction is reverse-biased. The larger size of the collector region helps in maintaining a higher breakdown voltage for the reverse-biased collector-base junction, preventing breakdown and ensuring the transistor's reliability.

By making the collector physically larger, the transistor's overall performance and characteristics are improved, making it an essential aspect of transistor construction.