There are several types of transistors. In this article, we shall delve deep into this topic and let you know more about the types of transistors, their characteristics, and their functions.
Transistors are essential electronic components that are utilized and used for switching, amplification, and processing of signals in electronic circuits.
Transistors come in two main types NPN (negative-positive-negative) and PNP (positive-negative-positive) We shall expound on this below.
In addition, We have two main categories of transistors – Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs).
Thousands of transistors fall under each of the two main types and categories above. We shall discuss these at length below.
In addition, remember that each type of transistor has its unique characteristics and can be utilized for different types of applications.
Transistors have several functions and characteristics. In this article, you shall learn more about transistor types as well as their functions and characteristics.
Characteristics of Transistors
Transistors have multiple characteristics – we shall look at them in an in-depth manner below…
Type – As noted above, there are two main transistor types… NPN and PNP. These types are determined by the arrangement of the semiconductor materials and the polarity of the voltage applied to the terminals.
Current Gain (hfe or β) – Current gain denoted by the symbols in brackets represents the ratio of the output current to the input current. A higher current gain is desirable for amplification purposes.
Voltage Ratings – A transistor has a maximum voltage rating that should not be exceeded to prevent damage. These ratings include the maximum collector-emitter voltage (Vce) and the maximum collector-base voltage (Vcb).
Power Dissipation (Pd) – For a transistor to work optimally, it has to operate within its maximum power handling without overheating.
Transition Frequency (ft) – this is a measure of the maximum frequency a transistor can operate as an amplifier. This measure represents the frequency at which the current gain starts to decrease.
Functions and Applications of Transistors
Different types of transistors have different types of functions and applications. Below we look into them in a detailed and comprehensive manner.
Amplification – widely used for signal amplification, transistors control a small input current or voltage and then amplify it to a larger current or voltage.
This transistor property is utilized in audio amplifiers, and frequency amplifiers, among other applications.
Switching – transistors can operate as electronic switches. In digital circuits, they can rapidly switch between on (conducting) and off (non-conducting) states.
In addition, this function has made it possible to create digital logic circuits and binary information processing in computers among other applications.
Signal Modulation – transistors are at the core of signal modulation in amplitude modulation (AM) and Frequency Modulation (FM) in radio communication.
Additionally, other communication modes utilize transistors for effective communication functionalities.
Voltage Regulation – when applied as voltage regulators, transistors stabilize and regulate voltage in electronic circuits. They maintain a constant output voltage despite variations in load conditions and input voltage.
Current Regulation – in applications such as current sources and constant current loads, transistors come in handy as they can control and regulate current flow in such circuitry.
Bipolar Junction Transistors (BJTs)
This is one of the main categories of transistors. Below we look at the main aspects of the Bipolar Junction transistors…
- Bipolar Junction Transistors do come in two main types – PNP (Positive-Negative-Positive) and NPN (Negative-Positive-Negative) configurations.
- Additionally, these transistors can be used for both switching and amplification of current, voltage, and signals
- BJT transistors are made up of and contain three layers of semiconductor material – the collector, the base, and the emitter.
- These must-have components are used as digital logic gates and in analog amplification circuits.
Field Effect Transistors (FETs)
This is the other main transistor category that you are bound to come across as you do your electronics.
Below are some of the major aspects of Field Effect Transistors.
- Field Effect Transistors are classified into three: MOSFET (Metal Oxide Semiconductor FET), JFET (Junction FET), and MESFET (Metal Semiconductor FET).
- In addition, FETs are voltage-controlled components and do not require a current to operate in the “on” state.
- JFETs are mainly in low-noise amplification circuits while MOSFETs are used in power and digital applications.
Types Of Transistors
Below we share with you a comprehensive and detailed list of the types of transistors you could come across as you do your electronics.
Kindly note that most of these transistors fall under the above-mentioned categories…
Metal Oxide Semiconductor Field Effect Transistors (MOSFETs)
If you have been in the electronics sphere for a while, I am sure you have come across some MOSFETs. I have and I like their phenomena.
What is it do you like about MOSFETs?
Well, MOSFETs fall under the FET transistors category. Below we describe some of the important MOSFETs aspects…
- They are the most common FETs and come in two variants – the N-Channel and the P-Channel.
- Furthermore, they can be classified into two modes – 1) Enhancement Mode – (normally off) and 2) Depletion Mode – (normally on).
- And yes, these transistors are extensively used in switching applications, voltage regulators, digital integrated circuits, and power amplifiers.
Junction Field Effect Transistor (JFET)
A JFET is a voltage-controlled transistor that has three terminals namely – Drain, Source, and Gate.
In addition, it is used for high-input impedance applications.
You are likely to come across them in low-frequency and low-power amplification circuits.
Metal Semiconductor Field Effect Transistors (MESFETs)
The metal semiconductor field effect transistors (MESFETs) are used in high-speed and high-frequency electronic applications such as microwave and radio frequency (RF) circuits.
In addition, they are made of gallium arsenide or other special materials and feature a metal-semiconductor junction.
Insulated Gate Bipolar Transistors (IGBTs)
IGBTs are powerful transistors because they combine the features of MOSFETs and BJTs under a single transistor.
In addition, they are suitable for high-current and high-voltage applications and are mainly used in the production of power inverters, motor drives, and switching power supplies.
Darlington Transistors
These types of transistors have a combination of two bipolar junction transistors (BJTs) connected in a specific way to achieve high current gain (amplification.
In addition, they are mostly used where a small control current needs to control a much larger load current.
Phototransistors
Like light-dependent resistors, phototransistors depend on light to control their operation and achieve their functionality.
They are mainly used in light-dependent applications like optocouplers, optical sensors, and light detectors.
Unijunction Transistors (UJTs)
These transistors have a unique construction that comprises a single PN junction and one emitter lead.
Additionally, unijunction transistors are used as pulse generators, relaxation oscillators, and timers.
Silicon Controlled Rectifiers (SCRs)
Though not traditional transistors, SCRs are semiconductor devices used for controlling high-power AC voltage.
They are commonly used in phase control and power regulation applications.
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