- Published 27 May 2024
- Last Modified 27 May 2024
- 6 min
Guide to Discrete Semiconductors
Explore Our Thyristors Guide: Understanding Their Functionality, Applications, and Types
It’s hard to imagine a world without discrete semiconductors. In this guide, we’re diving into this crucial component found in a wide array of circuits. We’ll cover what they are, how they differ from regular semiconductors, and the various types.
What is a Discrete Semiconductor?
To understand what a semiconductor is, let's first look at three terms used in electrical hardware: conductor, insulator, and semiconductor.
- Conductor: A material that allows the flow of electrons, enabling an electric current when a voltage is applied. Conductors have low resistance. Some are more efficient than others, hence their use in wiring. For instance, copper and aluminium are excellent conductors. Silver and gold top the list, but their cost limits their widespread use. Conductors become less effective as they heat up.
- Insulator: A material with high resistance, blocking the flow of electric current. Examples include plastic, rubber, glass, and wood. Plastic, being flexible and waterproof, is commonly used to insulate wiring.
- Semiconductor: Materials with conductivity between good conductors and insulators. They exhibit low resistance in certain conditions and high resistance in others, or they conduct electricity, though not very efficiently. These properties make them valuable in circuits for functions like amplification, switching, or current manipulation. Silicon, germanium, and tin are notable semiconductors, but there are many others when combined into compounds or alloys. The conductivity of semiconductors increases as they heat up.
That brings us to discrete semiconductors. As the name suggests, they are a specific type of semiconductor. In this case, it refers to semiconductor devices with a single fundamental function, as opposed to integrated circuit semiconductors with more complex functions.
Examples of discrete semiconductors include thyristors, Zener diodes, bipolar transistors, bridge rectifiers, and more – we’ll delve into each type below.
Exploring Discrete Semiconductors
Discrete semiconductors encompass a variety of components, including transistors, valves, rectifiers, and more. Some are available as modular accessories that can be easily integrated into existing circuits.
Certain discrete semiconductors are designed to perform functions similar to those of two separate devices connected in a specific configuration. This design optimizes space on a circuit board and provides essential functionalities that would otherwise require multiple components, all within a single component.
In discrete semiconductors, the arrangement of the semiconductors within the device largely determines their functionality. For instance, thyristors consist of four layers of semiconducting material with n- and p-type materials alternately sandwiched together.
Types of Discrete Semiconductors
Discrete semiconductors are fundamental components of electrical engineering, encompassing numerous types. Here are some common types of discrete semiconductors used in circuits, along with brief descriptions of their functions.
Thyristors
A thyristor is a semiconductor with two stable states, making it "bistable". It consists of four layers of semiconducting material, alternating between n- and p-type semiconductors. Its state can be altered by applying or removing a current, and once changed, it remains in that state until receiving another signal. Thyristors find applications as switches or latches, commonly seen in dimmer switches and power controllers.
Zener Diodes
Zener diodes allow electric current to flow in the opposite direction to normal when the current reaches a specific voltage known as the Zener voltage. They come in various Zener voltages or variable voltage designs. These diodes are widely used to limit voltage and provide protection against circuit overload or excessive voltage. They are essential components in power regulation and circuit protection.
Bipolar Transistors
Bipolar transistors are frequently used in analog circuits. In a circuit, they can act as switches, allowing a large voltage to pass through when a small signal voltage is applied. They are called bipolar because they utilize both negative and positive charges for operation. These transistors are present in integrated circuits but are also available as discrete units.
Bridge Rectifiers
A bridge rectifier is composed of diodes arranged in a specific configuration called a bridge. This setup converts alternating current (AC) input into direct current (DC), a basic function for most electronic devices. Bridge rectifiers work with a two-wire AC input, providing full-wave rectification.
MOSFET Transistors
MOSFET stands for Metal Oxide Semiconductor Field-Effect Transistor. These transistors are similar to bipolar transistors but require a tiny input voltage compared to bipolar types. They have four terminals, but typically only three are connected. MOSFETs are commonly used in various applications and are the most prevalent transistors in use.
TRIACs
TRIAC (Triode for Alternating Current) is a type of thyristor functioning as an electronic switch, conducting current bidirectionally. Once triggered by an input voltage, TRIACs allow current flow in both directions and remain in that state until another trigger switches them. They are comparable to a pair of silicone-controlled rectifiers in an inverse parallel configuration.
JFET Transistors
JFET (Junction-gate Field-Effect Transistors) are field-effect transistors controlling current flow with three terminals: source, drain, and gate. The gate regulates current flow, either restricting or blocking it based on voltage. They are commonly used in switching applications and can provide resistance dependent on voltage.
Schottky Diodes
Schottky diodes are made by combining a semiconductor with a metal and are known for their fast switching times and low turn-on voltage when used as switches. They are utilized in RF applications, power rectifiers, and preventing power discharge from batteries connected to solar panels.
DIACs
DIAC (Diode for Alternating Current) functions as a switch, maintaining its state until the signal voltage drops below a predetermined holding current, returning to a high resistance state and cutting off the circuit. They are used in dimmer switches and power overload protection systems.
Varactor Diodes
Varactor diodes, also known as Varicap diodes or tuning diodes, are semiconductor devices acting as capacitors controlled by the applied voltage. They are valuable in transmitters, TV sets, phones, and voltage-controlled oscillators, altering capacitance with changes in voltage. They only permit AC flow, with characteristics determined by the doping profile.
How Discrete Semiconductors Differ from Other Semiconductors
Numerous semiconductors are commonly integrated into circuits, often as part of an IC (integrated circuit). These circuits typically possess the capability to execute various functions within a device. This sets them apart significantly from discrete semiconductors.
A discrete semiconductor serves a singular, fundamental function that cannot be subdivided into other functions. In contrast, an IC may include a transistor, a diode, and other components, each capable of performing distinct functions independently or collectively as part of a circuit. However, a discrete semiconductor is limited to performing just one function. For example, a transistor solely functions as a transistor and cannot fulfill any other role.
In the contemporary landscape, the majority of semiconductors are procured as components of integrated circuits. Nevertheless, discrete semiconductors remain essential in specific applications, offering the most suitable solution to engineering requirements. Therefore, they play a crucial role in the electronic components market.
Given their discrete nature, certain semiconductors necessitate acquisition alongside other devices to achieve the desired functionality within a circuit. These semiconductor devices fulfill a spectrum of functions, from power regulation to serving as switches, among others. For certain engineering demands, the availability of discrete semiconductors renders prototyping and production economically viable.
