Introduction to Electronics

Introduction to Electronics

• Electronics focuses on the behavior and movement of electrons under electric and magnetic fields.
• The term "Electronics" highlights the importance of electrons in controlling electric energy in various devices.
• Electronics is defined as the science addressing electron motion and techniques to control electric energy through devices, applicable from simple circuits to advanced communication systems.
• Physical Electronics studies electron motion in mediums like vacuum, gas, and semiconductors.
• Electronics Engineering focuses on designing, fabricating, and applying electronic devices by integrating physical electronics principles for practical applications.
• Electronic circuits use active components like vacuum tubes, transistors, diodes, and integrated circuits, along with passive components and wiring.
• Circuits using active semiconductors with passive elements are known as electronic circuits.

Evolution of Electronic Devices

• The development of electronic devices is marked by three pivotal inventions: vacuum tubes, transistors, and integrated circuits.
• Vacuum Tubes: Thomas Edison's discovery of the "Edison Effect" in 1883 led to John Fleming's diode in 1897 and Lee de Forest's triode in 1906, which amplified electrical signals, though these devices were large and inefficient.
• Transistors: Invented in 1948 by John Bardeen, Walter Brattain, and William Shockley, transistors were smaller, more efficient, and required less power than vacuum tubes, marking a significant leap in electronics.
• Integrated Circuits (ICs): Proposed in 1952 by Geoffrey W. A. Dummer, integrating multiple transistors and passive components onto a single chip; mass-produced by the 1960s, leading to LSI and VLSI technologies in the 1970s for microcomputers and communication systems.

Applications of Electronic Devices

• Electronic devices are essential across sectors, enhancing functionality and efficiency.
• They play a crucial role in Rectification and Amplification. This is converting AC to DC current and increasing signal power.
• Electronic devices are important for Control, Power Generation, and Transmission, as well as the managing of signals and energy.
• Electronic devices have the ability to Convert electrical energy to light using LEDs and vice versa.
• Electronic circuits are critical for everyday functionalities in communication system like smartphones.
• They underpins navigation systems in healthcare (medical devices), control instruments, industrial systems, aerospace, and automotive sectors
• The future of electronic circuits is promising innovative developments in nanotechnology, quantum computing, and flexible electronics, revolutionizing industries and heralding the next generation of innovations.

Types of Electronic Circuits

• Electronic circuits are classified into three main types.
• Analog Circuits: Handles continuous signals, suitable for audio amplification and sensors.
• Digital Circuits: Operates on discrete binary signals (0s and 1s), forming the foundation of computing, including microprocessors and memory chips.
• Mixed-Signal Circuits: Incorporates both analog and digital elements, efficiently processing signals in devices like smartphones and embedded controllers.

Key Components of Electronic Circuits

• Resistors: Control the flow of current by providing resistance.
• Capacitors: Store and release electrical energy.
• Inductors: Store energy in a magnetic field when electrical current passes through them.
• Diodes: Only allow current to flow in one direction.
• Transistors: Act as switches or amplifiers in circuits.
• Integrated Circuits (ICs): Compact assemblies of multiple components on a single chip.

Basic Circuit Theory

• Electronic circuits operate based on fundamental electrical properties governing energy flow and interaction
• Key concepts include voltage, current, resistance, and impedance. Understanding these is essential
• Voltage (V): The Driving Force - Also known as electric potential difference, it pushes electric charges through a circuit; measured in volts (V).
• Ohm's Law: V = I × R, where V is voltage, I is current, and R is resistance.
• Current (I) – The Flow of Charge - Refers to the movement of electric charge; measured in amperes (A), representing the rate of charge flow.
• Direct Current (DC): Electric charges flow in one direction (e.g., battery), maintaining a consistent polarity of output voltage.
• Alternating Current (AC): Flow of electric charge periodically reverses direction (e.g., household power supply).
• Resistance (R) – Opposition to Current Flow - It is the property of a material that restricts the flow of electric current; measured in ohms (Ω). Higher resistance means less current flow and vice versa.
• Factors affecting Electrical Resistance:
  • Nature of the material: Conductors (e.g., copper) have low resistance, while insulators (e.g., rubber) have high resistance.
  • Length of the material: Longer wires have higher resistance.
  • Cross-sectional area: Thicker wires have lower resistance.
  • Temperature: Higher temperatures generally increase resistance.
  • Resistance is given by: R = ρ × (l/A) [ρ = resistivity of the material].
• Impedance (Z) – AC Resistance - It is the opposition to alternating current (AC), including capacitance and inductance effects; measured in ohms (Ω).
• Impedance formula Z=√R^2+(XL−Xc)^2 OR Z=R+jX
• Ohm's Law: Current in a circuit is directly proportional to the applied voltage and inversely proportional to the amount of resistance.
• Relationship of Current & Potential Difference: Current is directly proportional to potential difference.
• Current is expressed as: I = V/R
• Power (P) – The Rate of Energy Consumption
  • Power is the rate at which electrical energy is converted and it is measured in watts (W) and calculated using P = V × I
• Using Ohm's Law, power can also be expressed as: P = I^2 × R or P = V^2/R
• Example: A 100W electric light bulb connected to a 250V supply has a current of 0.4A flowing through it and a resistance of 625Ω.
• Power Consumption:
  • If water flows over a water wheel, the rate at which it turns is determined by both the water pressure (voltage) and the amount of water (current).
  • Electrical power similarly depends on both voltage and current.
• I-V Characteristic curves display the relationship between current flowing through a device and voltage applied across it, serving as a graphical tool for defining operating parameters.
• I-V curves illustrate how a device's performance changes under varying input conditions.
• Fixed resistors exhibit a linear relationship according to Ohm's Law (I = V/R), while components like LDRs and light bulbs show non-linear behaviors.

Multiples and Submultiples

• Currents, voltages, and resistances can be very large or small; multiples and sub-multiples of units are used.
  • mega (M): multiply by 1,000,000 (10^6) (e.g. 2 MΩ = 2,000,000 ohms)
  • kilo (k): multiply by 1,000 (10^3) (e.g. 10 kV = 10,000 volts)
  • milli (m): divide by 1,000 (10^-3) (e.g. 25 mA = 0.025 amperes)
  • micro (μ): divide by 1,000,000 (10^-6) (e.g. 50 μV = 0.00005 volts)
• Example 1: A p.d. of 20V applied to a resistor results in a current flow of 0.8A; the resistance is 25Ω.
• Example 2: A 2k resistor with a current of 10 mA flowing through it requires a p.d. of 20V.
• Example 3: With a resistance of 20 kΩ, a 100V battery yields a current of 5 mA; when the voltage is reduced to 25V, the current becomes 1.25mA.

Kirchhoff's Laws

• Kirchhoff's laws are important network theorems used in the analysis of electrical and electronics circuits.
• These laws are essential in the analysis of both direct current (DC) and alternating current (AC) circuits.
• Kirchhoff's Current Law (KCL) states that the algebraic sum of currents meeting at a junction is zero. The equation is ΣI = 0
• Kirchhoff's Voltage Law (KVL) states that the sum of voltages around a closed loop is always zero. The equation is Σ(I × R) + Σ(E.m.f's) = 0
• Procedure to apply Kirchhoff's Voltage Law to any circuits
  • Select any point in the circuit as a starting point.
  • Move along the circuit in a clockwise direction back to the starting point
  • Add algebraically the values of each voltage source and voltage drop across resistance, noting the correct sign (+ or -).
  • Equate the sum of the voltages in the circuit to zero after returning