Question

In a transistor, the base is very lightly doped as compared to the emitter because by doing so

• A. Base current is high.
• B. Recombination is decreased in the base region.
• C. The flow across the base region is mainly because of holes.
• D. The flow across the base region is mainly because of electrons.

Answer 1

The correct option is B

Recombination is decreased in the base region.

The explanation for the Correct Option:

Option (B):

1. In the emitter region, the majority of carriers are formed.
2. These majority carriers move towards the collector region through the base in the middle.
3. If the base is made highly doped, the majority of carriers will undergo a combination with the other carriers present in the base.
4. The number of carriers reaching the collector will be very less.
5. Therefore, the output collector current will be low.
6. Hence, the base is very lightly doped as compared to the emitter because by doing so recombination is decreased in the base region.

The explanation for Incorrect Options:

Option (C):

1. Doping of the base does not affect the type of carrier flow through the base. So, this option is incorrect.

Option (D):

1. Doping of the base does not affect the type of carrier flow through the base. So, this option is incorrect.

Option (A):

1. Since the base is very lightly doped, the number of carriers is very less.
2. Hence, the current from the base is not high.

Therefore, option (B) is the correct answer.