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Option 3 : (b), (c)
CONCEPT:
- Transistor: It is a semiconductor device that transfers a weak signal from a low resistance circuit to a high resistance circuit.
- The transistor is essentially a resistor that allows current to flow.
- The word transistor is a contraction of the current-transferring resistor.
- Transistors are commonly used in amplification, switching, and buffering signals or applied.
- There are two types of standard (bipolar junction) transistors, NPN and PNP.
DIAGRAM FOR NPN AND PNP TRANSISTORS:
- Transistors have three terminals namely Emitter, Collector, and Base.
| Sr .No | Emitter | Collector | Base |
| 1. | In a transistor, emitter supplies a large section of majority charge carriers. | In a transistor, the section that collects the majority of the charge carrier supplied by the emitter is called a collector. | The middle section of the transistor is known as the base. The collector-base junction is in reverse bias and offers higher resistance to the circuit. |
| 2. | The emitter is always forward biased with respect to the base so that it supplies the majority charge carrier to the base. | The collector-base junction is always reverse biased. | The base forms two circuits, the input circuit with the emitter, and the output circuit with the collector. The emitter-base is forward-biased and offers low resistance to the circuit. |
| 3. | The emitter of a transistor is heavily doped and moderate in size. | The collector section of the transistor is moderately doped, but larger in size so that it can collect most of the charge carrier supplied by the emitter. | The base of a transistor is lightly doped and very thin due to which it offers the majority charge carrier to the base. |
EXPLANATION:
- The key to the fabrication of a transistor is to make the middle layer, the base, as thin as possible without shorting the outside layers.
- It is customary to forward bias the emitter-base junction of a bipolar junction transistor as this increases the width of the depletion region whereas the base-collector junction is reverse biased.
From the above discussion, it is clear that,
The correct option is 3.
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