Question Video: Recalling the Doping Concentration of the Base of a Transistor | Nagwa Question Video: Recalling the Doping Concentration of the Base of a Transistor | Nagwa

# Question Video: Recalling the Doping Concentration of the Base of a Transistor Physics • Third Year of Secondary School

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The base of a transistor is ＿.

01:23

### Video Transcript

The base of a transistor is blank. (A) Heavily doped. (B) Moderately doped. (C) Lightly doped. (D) There is not enough information to determine the answer.

This question is asking us about the doping of the base of a transistor. Recall that transistors consist of three different parts: a collector, a base, and an emitter. When we draw these components for an npn transistor, it would look something like this. Regardless of transistor type, either npn or pnp, the doping present in the semiconductors that make it will be the same.

In our npn transistor, the collector and emitter will be much more strongly doped than the base. This is to say, the collector and emitter will have more impurities in their construction, which will result in a higher electrical conductivity. The base is much more weakly doped compared to the collector and emitter, meaning that electrical charge will have a more difficult time passing through it.

Also, for real transistors, not the diagrams we tend to use, the base is very thin. This thinness, combined with a low doping, helps minimize the chances for recombination of charge carriers in the transistor, which would otherwise increase the base current. Ideally, we want the base current to be much lower than the collector or emitter currents. Therefore, the base of a transistor is lightly doped. The correct answer here is (C).

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