Last Updated on October 23, 2023 by Kevin Chen
You are required to carry out an electronics project and one of the critical steps is getting the required tools and components. Transistors are among the electronic components that you should get for your project. Transistors come in different types and forms. Before you choose one, you need to ensure that it is a perfect fit for the project. So, how do I do this? Where should I start from?
The good news is as industry experts, we are here to help you. In this article, we are going to cover all that you should know on how to choose the right transistor for your project.
Compare the different transistor characteristics
As we have mentioned, there are different types of transistors in the market. How do I choose the best type and separate it from the rest? The easiest way is to compare their functions and properties. From there, you will be in a perfect position to know which type is the most suitable for your application area.
The three most common types of transistors are the Bipolar junction transistor (BJT), Field effect transistor (FET), and Metal-oxide semiconductor field effect transistor (MOSFET). Of the three types, which one should I pick?
We can only answer this by comparing their properties.
The bipolar junction transistor (BJT) is a type of transistor in which both holes and electrons serve as charge carriers. The physical structure of the BJT is characterized by three terminals which are the base, the collector, and the emitter. The base terminal always serves as the control terminal as it determines the amount of electric current or charges that will get into the transistor. The output will be based on the input current at the base terminal.
BJTs have three defined regions of operations. These are active region, cutoff region, and saturation region. At the active region, the transistor will be acting as an amplifier whereby it will produce high output current from a small input signal.
At the saturation mode, there is a maximum flow of electric charges on the transistor especially between the collector and emitter terminals. At this point, the transistor is in a forward bias mode.
So, when and where should I use the BJT transistor? Bipolar junction transistors are mainly used in applications that require fast switching speed and as well as high current gain. They are also suitable for sensitive applications in which electric noise is a key factor. These applications include audio circuits and analog amplifiers.
Field-effect transistors are equally as common as the BJTs. FETs have the full capacity to control the flow of electric charges in circuits. By doing so, they help to determine the output of the circuit. They also have three terminals named as the source, the gate, and the drain.
FET operates in two defined modes; linear mode and saturation mode. Linear mode is similar to the saturation mode in the BJT.
So, where are these transistors used? FETs are perfect for applications that have high input impedance, and low power consumption, and also for the applications in which you need high input impedance. They are also a perfect fit for the project in which you need to achieve a high-frequency response.
This is another type of transistor that you are likely to end up using for your project. Metal-oxide semiconductor field effect transistor shares numerous features with field effect transistors (FET). The main difference is it uses a metal-oxide layer to provide insulation at the gate terminal.
MOSFETs have four terminals which are the source, the gate, the drain, and the body. They have three modes of operation which are the enhancement mode, depletion mode, and the inversion mode.
Why should I use MOSFET transistors for my project? Do you want to achieve ultra-high switching speed on your application? A MOSFET transistor may be an ideal choice for you. These transistors are also perfect if your project entails building microcontrollers and digital logic circuits.
Now that you know the three main types of transistors and their properties, we can proceed to look at other factors that are likely to determine the transistor that you should choose for your project.
Know the transistor configurations
Regardless of the type and uses of transistors, you should pay close attention to the configuration of the transistors that you intend to use on your project. Transistor configuration refers to the arrangement of the semiconductor materials in the structure of a transistor so that it operates on the modes that we have just defined.
The different transistor configurations include common emitter (CE), common base (CB), and common collector (CC) configurations. Each of these transistor configurations is designed to achieve a specific goal when included in a circuit. This is based on the fact that different transistor configurations come with different input and output characteristics. Also, each transistor configuration comes with its set of advantages and disadvantages.
Before you choose any transistor for your project, establish its configuration so that you can find out whether it will be suitable for your application area.
What will be the work of transistors in your project?
At this point, you are sure of the type and configuration of the transistor. The next factor that will define your choice is the application of the transistor. What do you intend the transistor to achieve that no other electronic component can achieve?
Common applications of transistors in electronics include amplifiers, switches, logic gates, oscillators, sensors, signal converters, and current regulators, among others.
It will be easier to make the right choice of transistor type and specifications only after confirming the role that the transistor will play in an electric circuit or even the general application.
Now that you know the type, configuration, and purpose of the transistors for your project, the next step entails confirming the key parameters of the transistor. The technical data or specs will determine the overall performance of the transistor. They also dictate the suitability of the transistor in your project.
Some of the technical parameters that you should know include:
The current gain of a transistor refers to the ratio of the base current to the collector current. It determines the amplifying capacity of the transistor and is indicated by the symbol β. If you intend to use the transistor as an amplifier, it is advisable to choose one with the highest current gain.
This is the maximum voltage that can be handled at the collector-emitter junction of the transistor. In most transistors, it usually ranges around 30 volts or more. Exceeding the Vce value can damage the transistor.
Emitter-base voltage (Vebo)
This is the maximum voltage that can be applied at the emitter-base junction of the transistor. It is usually lower than Vceo and in most transistors, it is 6 volts.
Collector-base voltage (Vcbo)
This is the maximum voltage that can be applied at the collector-base function. The value of this voltage is determined when the emitter circuit is open.
Total power dissipation
This is the amount of power that is released by the transistor. It is measured in watts and depends on the size of the transistor. You can get the total power dissipation by multiplying the collector current and the voltage across the transistor.
This is the current the current that can be allowed to flow through the collector terminal of the transistor.
Transistor supplier and manufacturer
One key factor that most people tend to ignore is the source of the transistors. Where do you plan to buy transistors for your project? The source of the transistor matters as it will dictate the quality of the transistor that you will get. Most of us prefer to buy from reputable transistor manufacturers and suppliers. It gives us an assurance that you are likely to end up with the right transistor for the job.
But, how do I know that a particular manufacturer or supplier is the right one? You will have to take your time and conduct some deep research about each transistor manufacturer and supplier that you encounter. Check out their reviews so that you can know what other people are saying about them.
This sounds like too much work, right? Especially when you are in a different country and you intend to import transistors from China. There is a perfect solution to this; buying through reputable electronic components sourcing agents in China. These are experienced entities that specialize in ordering electronic components such as transistors on behalf of their clients. All you need is to find such a sourcing agent and they will do the rest of the sourcing task on your behalf.
With the points that we have discussed here, you should be in a perfect position to choose the best transistors for your project. Keep in mind that the right transistor will guarantee the success of your project. On the other hand, a wring transistor will be a major source of frustration. Consider all the factors that we have mentioned and you will be sure of getting the best transistors for electronic projects.
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