Transistor Explained

Transistors are at the top-notch position in today’s electronics technology. The improvement of transistors has brought about numerous progressions to the world. Everything from cell phones to vehicles utilizes them to work effectively. 

In this article, we won’t dive too profoundly into semiconductor material science; however, we’ll get profound enough into the subject that you will see how a transistor act as an enhancer and as a switch.

Transistor Definition, Construction, Symbols

Transistor Definition 

A transistor is an electronic one equipped for controlling the current or voltage stream and goes about as a switch or door for electronic signs. It comprises of three layers of semiconductor material, each equipped for conveying a current. 

These semiconductor materials are given extraordinary properties by a concoction cycle known as doping. The doping cycle either adds additional electrons to the material or makes openings in the material’s precious stone structure.

Transistor Construction

There are two types of widely used transistors, and they are Bi-Polar junction (BJT) and metal-oxide field-effect (MOSFET). In this article, we will focus on BJT because it is slightly easier to understand.

Transistors are developed by initiating three different layers of semiconductor materials within a group. Semiconductor materials with extra electrons are called an n-type and material with electrons removed is called a p-type. 

The NPN transistor is intended to pass electrons from the producer to the gatherer. The producer emanates electrons into the base, which controls the number of electrons the producer transmits. A large portion of the electrons radiated is gathered by the gatherer, which at that point sends them along to the following piece of the circuit.

In a  PNP transistor, the base still controls the flow of current, but the current flows in the opposite direction (emitter to collector). Here, instead of electrons, the emitter emits holes. 

Transistor Symbol

A transistor is nothing but it is a terminal device and the pins are Collector (C), Base (B), and Emitter (E). The circuit symbols for both NPN and PNP BJT may vary.

The only difference in the NPN and PNP transistor circuit symbol is in the direction of the arrow on the emitter. The arrow on the NPN points out and on the PNP it points in. 

Transistor Functionalities

A transistor can produce a stronger output signal, a voltage, or a current, which is proportional to the weaker input; thus, it can act as an amplifier. Then again, they can be utilized to turn the flow on or off in a circuit as an electrically controlled switch, where other circuit components decide the measure of power.

Transistor has four regions of operation out of which active, saturation, and cut-off are most commonly used. A transistor as an amplifier works in the active region. When a transistor works as a switch, it works in the cut off and saturation regions. Both emitter-base junction and collector-base junction remains the same at a saturation region. But in peak time, both junctions are forward biased.