BIPOLAR TRANSISTOR Meaning and
Definition
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A bipolar transistor refers to a three-layer semiconductor device that consists of two types of doped regions, namely the p-type and n-type, forming a PNP or NPN structure. It is a fundamental component of electronic circuits used for amplification and switching purposes. The bipolar transistor operates based on the principles of both majority carrier and minority carrier currents within the device.
The transistor consists of three terminals: the emitter, base, and collector. The emitter is heavily doped to enhance the number of majority charge carriers, while the base is lightly doped to provide a narrow region for minority charge carriers transportation. The collector is moderately doped and located on the opposite side of the emitter.
When an input signal is applied to the base-emitter junction, it causes a change in the bias and controls the current flow through the device. In the case of an NPN transistor, a positive voltage applied to the base-emitter junction allows current to flow from the emitter to the base. This action induces an amplified current flowing from the collector to the emitter. On the other hand, in a PNP transistor, a negative voltage applied to the base-emitter junction results in current flowing from the base to the emitter. Consequently, an amplified current flows from the emitter to the collector.
Bipolar transistors are widely utilized in a multitude of applications such as audio amplification, radio frequency amplification, digital logic circuits, power switching applications, and signal modulation, among others. They provide excellent performance in terms of higher gain, power handling, and their capability to operate at high frequencies.
Etymology of BIPOLAR TRANSISTOR
The word "bipolar transistor" combines two different terms from electronics and physics.
The term "transistor" is a combination of "transfer" and "resistor". It was coined by John R. Pierce, a physicist at Bell Laboratories, while working on the invention of the device. The term "transfer" refers to the process of transferring an electrical signal from one circuit to another, while "resistor" signifies the device's ability to regulate the flow of current. Together, "transistor" thus denotes an electronic component that transfers electrical signals while controlling the flow of current.
The term "bipolar" in "bipolar transistor" refers to the two types of charge carriers involved in the operation of this particular transistor.
