The transistor topic can be hard to understand. Here I would like to explain in simple words how a Bipolar Junction Transistor works. I will also provide a simulation result to make the understanding better. The picture below shows how a small current at the base allows a large current to flow from collector to emitter ( electron flow from emitter to collector)
A BJT is a three terminal current controlled device made from combining n and p type semiconductors.It can be used for two main functions which are :
The Base region plays the main role as the "guard" that controls the flow of current from Emitter (E) to Collector (C). We can use the analogy of sink tap where the Base is the tap head , the inlet as the Emitter and outlet as Collector. The tap head can be used to regulate the opening that allows water to flow ( similar to current) from inlet to outlet.
By applying current to the Base, a transistor can be operation in three regions:
In order to use transistor as a switch, merely to ON or OFF, the transistor will be operated in cutoff or saturation region.
For amplification purpose, the transistor will be biased to operate in the active region, where the linear relationship between base current and collector current is defined by Ic=BIb ( Beta is the current gain or hfe).
The above is the basic explanation of transistor. In the video, I will show you how by changing the current to the base of a transistor, the different operational region can be achieved.
