Transistor Working


The transistor refers to simple components that are mostly used to build different types of electrical devices and different projects. It is an electronic device that is mostly applicable in the electric circuit to amplify the electrical signals as well as allows it as a wide array of electrical devices. The transistor is classified into three different categories like emitter, base, as well as collector. The principal idea that is behind the construction as well as the working principles of the transistor is based on the current flow to the electric circuit.

What is a transistor?

The characteristics of the transistor are classified into three different categories like input characteristics, output characteristics, and current transfer characteristics. Input characteristics of a transistor describe that value-changing rate in reference to the input voltage when the voltage is constant while output characteristics of a transistor refer to the curve that is obtained by plotting the output current that is against the output voltage when a constant current flowing through the transistor (Huang et al. 2019).

The current transfer characteristics of a transistor refer to an input device that guides to keep the output voltage and input current constant.

Figure 1: Construction of a transistor

Types of transistor

Several types of transistors are available for use and each type of transistor is used for a specific purpose. The classification of transistors can be categorized into two different types BJT and FET. Bipolar Junction Transistor is commonly known as the BJT and it is just a normal transistor that has two different types of configurations NPN as well as PNP. Field Effect Transistor is commonly known as FET and it is mainly used as a voltage-controlled device. The principal advantage of this type of transistor is that it consists of a high input device (Gao et al. 2019). It is measured by the Mega Ohms and it consumed lower power than other types of transistors.

Working principle of a transistor

The working principle of the transistor proceeds with an anti-parallel diode that forms innovative electronic components that are called components. During the working time, the transistor does not follow the ohms’ law.

Figure 2: Working principle of a transistor

During working three different components of the transistor such as emitter, base as well as collector works s a unit. There are two different types of barriers seen during the working process forward and reverse barriers.

Composition of a transistor

A transistor consists of three main parts.

  • The negative lead (Emitter) − This part of a transmitter helps in emitting free electrons to the transmitter’s base. This is also used in form of a buffer amplifier in reducing loads of a previous stage. This part also provides a lower rate of independence which is related to the output of a circuit. The emitter-based circuit is associated with forwarding biased. This also offers a low range of resistance to a circuit.
  • The positive lead (Collector) − This part of a transmitter takes all the electrons which are emitted from the transistor base. This side of a transistor is slightly doped in contrast to an emitter (Huang et al. 2019). The thickness of a collected is greater than an emitter. There is a junction within the collector that helps in gathering most of the charge carriers that are sent by emitters, present in a transistor.
  • Base − Most of the electrons that are injected are passed to the collector with the help of a transistor base. A significant interaction between collector and emitter is brought by the base region (Latella et al. 2019). This portion is the middle section of a transistor. Two individual circuits are formed in that place. The emitter acts as an input circuit and the collector acts as an output circuit.

Application of the transistor

In current times, transistors are used in various aspects. A semiconducting material is used in the formation of a transistor. Both conductive and non-conductive materials are also used.

Integrated circuits

In an integrated circuit, resistors, diodes, transistors, and capacitors are combined. A chip, made of a silicon wafer is used in combining these. This chip is known as a microchip. In the formation of an integrated circuit, transistors are highly used. An integrated circuit is useful as it consumes very less energy. This is very small as well which is why the size of a circuit is very small and the making cost is low as a result.

Figure 3: P-N-P transistor

Heat-operated switch

Transistors are used in fire alarms. An important component of a heat-operated switch is a transistor. Based on the surrounding temperature, this resistor responds (Yang et al. 2020). In the case of a high temperature, the resistance of a transistor decrease and the exact opposite is found for a low temperature.


The circuit of the transistor depends on the three different types of configurations that are the common emitter transistor, common base transistor, as well as common collector transistor. These three circuit configuration of the transistor has their individual characteristics curve. The type of circuit configuration of the transistor is selected based on the requirement of the electric device.


Q1. What is the main characteristic of a bipolar junction transistor?

In a bipolar junction transistor, two different PN junctions are available. This controlled device is an important example in which the functions of a transistor are seen.

Q2. How many terminals are there within a transmitter and what are they?

There are a total of three terminals. The emitter, collector, and main base are the important terminals, used in a transmitter.

Q3. How many PON junctions are there in Bipolar Junction Transistor?

There are a total of two junctions. PNP and NPN is these two junctions that are informer parts for the sake of convenience.

Q4. Which kind of device is a FET?

FET is such kind of transistor that is associated with a unipolar device. This device is made with any of the materials between n-type and p-type.


Simply Easy Learning

Updated on: 13-Oct-2022


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