Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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In a Transistor, - Physics

MCQ

In a transistor,

Options

  •  the emitter has the least concentration of impurity

  • the collector has the least concentration of impurity

  • the base has the least concentration of impurity

  • all the three regions have equal concentrations of impurity.

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Solution

the base has the least concentration of impurity

When the emitter of a transistor is forward biassed, the majority carriers move from the emitter to the collector through the base. As the base is thin and lightly doped, only small amount of a combination of electrons and holes takes place, leading to weak base current. This makes the collector current equal to the emitter current.
If we make any other choice for least concentration of impurity, we will have a low value of collector current. Thus, the purpose of a transistor will not be fulfilled.

Concept: Energy Bands in Conductors, Semiconductors and Insulators
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APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 23 Semiconductors and Semiconductor Devices
MCQ | Q 14 | Page 418
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