Question

For the functioning of a transistor its emitter-base junction has to be:

Answer 1

Step 1: Forward Biasing

1. In an unbiased p-n junction there exists an intrinsic potential barrier that tends to oppose the movement of majority holes from p-side to n-side and that of majority electrons from n-side to p-side.
2. Now if an external voltage is applied in such a way that the p-side becomes positive and the n-side negative then the intrinsic potential barrier is reduced.
3. The junction is then said to be forward-biased.
4. Now a good number of holes from the p-side will be able to overcome this reduced potential barrier and diffuse into the n-side.
5. Similarly, a good number of electrons from the n-side will be able to cross the reduced barrier and diffuse into the p-region.
6. These two flows constitute a large current in the same direction, called forward current which increases exponentially with the applied voltage.

Step 2: Explanation of transistor

1. A transistor is an electrical component that is responsible for regulating the current or voltage flow in a circuit.
2. It acts as a gate or switch for electrical signals.
3. It is made up of semiconductor materials.
4. If a layer of p-type material is sandwiched between two n-type layers, this is called an n-p-n type transistor as shown in the figure.
5. On the left-hand side, we have the emitter, in the middle, we have the base, and on the right-hand side, we have the collector.
6. For forward bias, the majority of charge carriers cross the junction, and hence current flows through the circuit.
7. For reverse bias, the minority charge carriers flow across the junction and hence the current flow is very low (almost negligible).
8. Thus, the proper amount of current flows through the transistor, or the proper functioning of the transistor takes place when the transistor is forward-biased.

Therefore, the functioning of a transistor its emitter-base junction has to be forward biased.