Where is base on transistor

In the beginning of 20 th century when the vacuum triode was invented, it was considered as the significant development in the field of electronics. This is because devices such as computers were entirely based on them.

But the problem started with their size which can capture the entire room. Now you can imagine what will happen if the entire room consists of a single processing system.

Obviously, to work with it is a cumbersome process. Fortunately, we have compact size processing system in the contemporary world. But this all has become possible with the invention of the transistor. The consequences are quite evident. Now, all the computing devices are available in small size which we can easily carry with us anywhere. A diode is two terminal device, thus, if we merge the two diodes provided that one terminal is common, the resulting device will comprise of three terminals.

This is how a transistor is constructed. We can use either sandwiched P-type layer of the semiconductor between two N-type semiconductors or by sandwiching N-type layer between two P-type semiconductor specimen. A transistor is a semiconductor device, so the semiconductor material used in its construction can be either germanium or silicon, but silicon is preferred over germanium because it possesses smaller cutoff current.

The base of the transistor is very thin and lightly doped because of which it has less number of electrons as compared to the emitter. The few electrons of the emitter are combined with the hole of the base region and the remaining electrons are moved towards the collector region and constitute the collector current. Thus we can say that the large collector current is obtained by varying the base region. When the emitter junction is in forward biased and the collector junction is in reverse bias, then it is said to be in the active region.

The transistor has two junctions which can be biased in different ways. The different working conduction of the transistor is shown in the table below. FR — In this case, the emitter-base junction is connected in forward biased and the collector-base junction is connected in reverse biased. The transistor is in the active region and the collector current is depend on the emitter current. The transistor, which operates in this region is used for amplification. FF — In this condition, both the junction is in forward biased.

The transistor is in saturation and the collector current becomes independent of the base current. The transistors act like a closed switch. RR — Both the current are in reverse biased. The emitter does not supply the majority charge carrier to the base and carriers current are not collected by the collector. Thus the transistors act like a closed switch. RF — The emitter-base junction is in reverse bias and the collector-base junction is kept in forward biased. As the collector is lightly doped as compared to the emitter junction it does not supply the majority charge carrier to the base.

Hence poor transistor action is achieved. Transistors are an essential component in many circuits and are sometimes used to amplify a signal. Transistors can be regarded as a type of switch, as can many electronic components. Transistors are manufactured in different shapes but they have three leads legs.

Diagram 'A' shows an NPN transistor which is often used as a type of switch.