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Which of the following statements is correct about a transistor?
Emitter region is much thinner as compared to base and collector.
All the three regions emitter, base and collector have the same size.
Collector region is much thinner as compared to emitter and base.
Base region is much thinner as compared to emitter and collector.
Base region is much thinner as compared to emitter and collector.
In a Bipolar Junction Transistor (BJT), the base region is manufactured to be extremely thin compared to the emitter and collector regions. This specific structural design is essential to ensure that the majority of charge carriers injected by the emitter pass through the base into the collector with minimal recombination.
In a Bipolar Junction Transistor (BJT), the base region is manufactured to be extremely thin compared to the emitter and collector regions. This specific structural design is essential to ensure that the majority of charge carriers injected by the emitter pass through the base into the collector with minimal recombination.
Think of the base like a thin, loose-mesh screen door; it is easy for the wind (charge carriers) to blow right through it into the house (collector) without getting stuck, whereas a thick wall would block the flow.
E-B-C Size Order: Emitter (Big/Heavily doped), Base (Tiny/Lightly doped), Collector (Biggest/Moderately doped).
IEтАЛ=IBтАЛ+ICтАЛ тАФ The fundamental current relationship where emitter current is the sum of base and collector currents.
╬▓=IBтАЛICтАЛтАЛ тАФ Current gain factor, representing the ratio of collector current to base current.
The emitter is heavily doped to provide a high concentration of charge carriers. The base is lightly doped and very thin so that most carriers injected from the emitter gain enough kinetic energy to cross the depletion layer of the collector-base junction before recombination can occur. If the base were thick, recombination would consume the charge carriers, reducing the current gain (╬▓) of the transistor.
Emitter is heavily doped to supply maximum charge carriers.
Collector is physically the largest region to dissipate heat generated during operation.
Base must be thin (typically 10тИТ6 m) to minimize recombination of charge carriers.
High current gain efficiency due to thin base region.
Compact size suitable for modern integrated circuits.
Sensitive to temperature fluctuations.
Limited switching speed compared to field-effect transistors.
Electronic switching in digital logic circuits.
Signal amplification in audio and radio systems.
The emitter-base junction is forward-biased, while the collector-base junction is reverse-biased for normal operation.
Option A is incorrect because the emitter is medium-sized; Option B is incorrect as doping levels and sizes vary; Option C is incorrect because the collector is the largest region for heat dissipation.
D is correct тАФ The base region is made very thin (often less than 1╬╝m) to ensure efficient transfer of charge carriers from the emitter to the collector.
Always remember the 'E-B-C' mnemonic for doping: Emitter (Heavy), Base (Light), Collector (Moderate); and for size: Collector > Emitter > Base.