Transistor Currents Explanation

Transistor Currents:

Transistors are nothing but a transferred resistor. It is a semiconductor device which is used to amplify a signal. Some time it is used in switching operation. In our last study we have seen, the transistor working principle, at we have finished at the type current flow. But in this we are going to talk about the transistor currents. Let’s begin the transistor current article.

Transistor current:

There are three different types of currents are flows in a transistor. Which are

• The current flow through emitter terminal is called Emitter current and it is denoted by I_E
• The current flow through the collector terminal is called collector current, It is symbolized by I_C
• Like that I_B is referred to base current which flows through base terminal.

Here the direction of conventional current is always opposite to flow electron current, since

Also once again recall that a few parts of charge carriers from emitter recombine with holes in base region and remaining charge carriers flow through the collector. Therefore, almost all of I_E crossed to the collector and small portion of I_E flows into the base terminal. The current that leaves collector base junction α_dc * I_E and the value of α_dc is typically 0.96 to 0.99.

In NPN transistor, junction J2 (collector-base) will be reverse biased, therefore there is a reverse leakage current I_CBO (collector-base leakage current) flows towards the collector terminal. In PNP transistor the current flows due to the holes moving from n-types base to p-type collector.

Now the collector current is sum of the portion of I_E which flows across the collector-base junction and the reverse saturation current. hence

Since I_CBO << I_C

Therefore, α_dc is approximately equal to the ratio of collector current and emitter current. α_dc is also referred to as the common base current gain.

Video Explanation of Transistor Current: