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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The collector of a transistor is _____ doped.
Heavily
Moderately
Lightly
None
Moderately
Quick Summary: In a Bipolar Junction Transistor (BJT), the collector is moderately doped. This specific doping level is chosen to provide a balance between the need for a large depletion region to handle high reverse-bias voltages and the requirement for efficient charge collection.
In a Bipolar Junction Transistor (BJT), the collector is moderately doped. This specific doping level is chosen to provide a balance between the need for a large depletion region to handle high reverse-bias voltages and the requirement for efficient charge collection.
NE>>NB<NC
Width_{Collector} > Width_{Emitter} > Width_{Base}
The emitter is heavily doped to inject a large number of charge carriers into the base. The base is very thin and lightly doped to minimize recombination of carriers. The collector is moderately doped, significantly larger in size than the emitter, and acts as the region where carriers are gathered, requiring a wider depletion layer to prevent junction breakdown under reverse bias.
Emitter doping is highest (NE) to maximize injection efficiency.
Base doping is lowest (NB) to minimize recombination and facilitate base-width modulation.
Collector size is largest to dissipate heat generated during operation.
Collector doping (NC) is kept moderate to maintain a high breakdown voltage (VBR).
Allows for high power dissipation due to large junction area.
Ensures high reverse breakdown voltage due to moderate doping.
Higher collector doping than base leads to smaller depletion width compared to an intrinsic region, though still larger than emitter.
Switching circuits
Power amplification
Signal processing
Emitter: Heavily doped for high carrier injection.
Base: Lightly doped and narrow to ensure most carriers reach the collector.
Collector: Moderately doped to handle higher voltage levels.
Option A (Heavily) describes the Emitter.
Option C (Lightly) describes the Base.
B is correct — The collector is moderately doped to balance charge collection efficiency with the necessity for a high collector-base junction breakdown voltage.
Always remember the mnemonic 'EHC' for Emitter (Heavily), Base (Lightly), Collector (Moderately) regarding doping concentration.