Key Electronic Components: Function and Applications

Transistors: Function and Types

The transistor is one of the most widely used electrical components, primarily made of semiconductor materials. Its main characteristic is its ability to amplify electric current.

Transistors typically have three terminals:

• Emitter (e)
• Collector (c)
• Base (b)

There are two main types of bipolar junction transistors (BJTs): NPN and PNP. Their fundamental function involves current amplification: a small current flowing through the base terminal controls a much larger current flowing between the collector and emitter terminals. The amplified current, along with the base current, typically flows out through the emitter (for NPN transistors) or into the emitter (for PNP transistors), with the collector handling the larger controlled current.

Light Dependent Resistors (LDRs) Explained

Light Dependent Resistors (LDRs), also known as photoresistors, are components whose resistance changes significantly with the intensity of light striking them. They are fundamental electrical components made from semiconductor materials.

LDRs exhibit a variable resistance that depends on the amount of light they receive: their resistance decreases as light intensity increases. One common application is in light-sensing circuits, such as those used to automatically turn lights on at dusk and off at dawn, based on ambient light intensity. They can also be used to activate motors or other devices in response to changes in light levels.

Printed and Integrated Circuits

Printed Circuit Boards (PCBs)

Printed Circuit Boards (PCBs) are platforms where electronic components are mounted and interconnected. Components are inserted or placed onto a non-conductive board that has conductive pathways, often called traces, etched or printed onto it. These traces establish the electrical connections between the various components, forming a functional circuit.

Integrated Circuits (ICs)

Integrated Circuits (ICs), also known as microchips or chips, are miniaturized electronic circuits that incorporate a vast number of electronic components (like transistors, diodes, and resistors) on a small piece of semiconductor material, typically silicon. They represent a significant advancement in electronics, allowing for complex functionalities in compact sizes.

Material Electrical Behavior

Materials can be classified based on their ability to conduct electric current:

• Conductors: These materials readily allow electric current to flow through them. Examples include metals like copper and silver.
• Insulators: These materials strongly resist the flow of electric current. They do not allow current to circulate easily.
• Semiconductors: These materials have electrical conductivity between that of conductors and insulators. Under normal conditions, they might act as insulators, but under specific conditions (e.g., application of voltage, temperature changes, or doping with impurities), they can conduct electricity. Examples include silicon (Si) and germanium (Ge).

  Semiconductors are of paramount importance in modern electronics as they are the foundational materials used to manufacture essential components like diodes, transistors, and integrated circuits.

  Key Characteristics of Semiconductors:

  • Their conductivity can be controlled. For instance, when the applied voltage or energy is below a certain threshold, a semiconductor may behave as an insulator.
  • When the applied voltage or energy exceeds that threshold, it can transition to behave more like a conductor.

Diodes: Unidirectional Current Flow

A diode is an electronic component typically made from semiconductor materials. Its primary characteristic is that it allows electric current to flow predominantly in only one direction while blocking current flow in the opposite direction.

When a diode is forward-biased (powered appropriately), it permits current to pass through it. The arrow in the diode's circuit symbol indicates the direction of conventional current flow (from anode to cathode). If current attempts to flow in the reverse direction (from cathode to anode), the diode exhibits high resistance and effectively blocks the current, meaning it does not conduct significantly.

Key Diode Applications: Rectification

One of the most significant applications of diodes is in rectification, which is the process of converting alternating current (AC) into direct current (DC). This application is crucial because many electronic devices and appliances, such as computers (PCs), televisions (TVs), and various other electrical equipment, require DC power to operate, even though they may be powered from an AC mains supply.

Light Emitting Diodes (LEDs)

A Light Emitting Diode (LED) is a special type of diode that is widely used in modern technology. Its defining characteristic is its ability to emit light when electric current passes through it. LEDs can produce light in various colors, depending on the semiconductor materials used in their construction.

Physically, LEDs typically have two leads (often referred to as legs). One lead is usually shorter than the other. The shorter lead generally indicates the cathode (negative terminal), while the longer lead indicates the anode (positive terminal). This helps in correctly orienting the LED in a circuit.