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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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In an npn transistor, _____ are the minority carriers.
Free electrons
Holes
Donor ions
Acceptor ions
Holes
Quick Summary: In an npn transistor, the majority charge carriers are free electrons because the emitter and collector are n-type doped regions, while the base is p-type. Consequently, holes act as the minority charge carriers within the n-type regions and are the majority carriers only in the p-type base region.
In an npn transistor, the majority charge carriers are free electrons because the emitter and collector are n-type doped regions, while the base is p-type. Consequently, holes act as the minority charge carriers within the n-type regions and are the majority carriers only in the p-type base region.
ni2=n×p — Mass Action Law representing the relationship between carrier concentrations in semiconductors
The transistor structure consists of two n-type regions sandwiching a p-type region. Due to the high doping concentration in the emitter and the base-emitter junction being forward-biased during operation, current flow is primarily governed by electrons injecting from the emitter to the base; however, the intrinsic property of the n-type silicon itself dictates that electrons are the majority carriers and holes are the minority carriers.
An npn transistor uses electrons as the primary charge carriers for current conduction.
Minority carriers in n-type material are always holes, regardless of whether it is part of a diode or transistor.
Thermal energy generates electron-hole pairs, establishing the minority carrier concentration.
Minority carrier current is highly temperature-dependent, leading to thermal instability in transistors.
High electron mobility leads to faster switching speeds.
Commonly used in integrated circuits due to manufacturing efficiency.
Minority carrier current can increase significantly with temperature, potentially causing thermal runaway.
Switching circuits
Amplifier stages
Logic gates in digital electronics
In npn transistors, the minority carriers (holes) in the emitter/collector regions contribute to the leakage current ICBO.
Option A is incorrect because free electrons are the majority carriers in the emitter and collector regions.
Options C and D refer to dopant ions fixed in the crystal lattice, which do not contribute to charge carrier current flow.
B is correct — Holes act as the minority charge carriers in the n-type emitter and collector regions of an npn transistor.
Always remember that in any semiconductor region, if electrons are majority, holes are minority, and vice versa. This rule applies universally to diodes and all BJTs.