An overview of basic electronics principles, components, and circuits. Students will learn about voltage, current, resistance, and how to read electronic schematics.
Introduction to Electronics – Quick Reference Notes
1. What Is Electronics?
- Definition: Branch of physics and engineering that deals with the flow and control of electrons in various media (conductors, semiconductors, vacuum).
- Goal: Design, analyze, and build circuits that process information, power devices, or sense the environment.
- Key Idea: Use components (resistors, capacitors, transistors, etc.) to manipulate voltage, current, and charge.
2. Basic Electrical Quantities
| Quantity |
Symbol |
Unit |
Relationship |
| Voltage (Potential Difference) |
V |
Volt (V) |
Energy per charge |
| Current (Flow of Charge) |
I |
Ampere (A) |
Charge per time |
| Resistance |
R |
Ohm (Ω) |
Opposition to current |
| Power |
P |
Watt (W) |
( P = VI = I^2R = \frac{V^2}{R} ) |
| Capacitance |
C |
Farad (F) |
Ability to store charge |
| Inductance |
L |
Henry (H) |
Ability to store magnetic energy |
3. Fundamental Laws
- Ohm’s Law
[
V = I \times R
]
- Kirchhoff’s Voltage Law (KVL)
Sum of voltages around any closed loop = 0.
- Kirchhoff’s Current Law (KCL)
Sum of currents entering a node = sum leaving it.
- Power Law
[
P = V \times I
]
4. Core Components
| Component |
Symbol |
Function |
Typical Use |
| Resistor |
R |
Limits current, drops voltage |
Biasing, voltage dividers |
| Capacitor |
C |
Stores electric charge |
Filtering, timing, coupling |
| Inductor |
L |
Stores magnetic energy |
Filters, energy storage, transformers |
| Diode |
D |
Allows current in one direction |
Rectification, protection |
| Transistor (BJT/ MOSFET) |
Q |
Switches or amplifies signals |
Logic gates, amplifiers |
| Integrated Circuit (IC) |
– |
Combines many transistors & passive parts |
Microcontrollers, op‑amps, logic families |
5. Types of Circuits
| Category |
Description |
Example |
| Passive |
Only resistors, capacitors, inductors (no gain) |
RC low‑pass filter |
| Active |
Contains active devices (transistors, ICs) |
Op‑amp amplifier |
| Digital |
Binary logic levels (0/1) |
Microcontroller board |
| Analog |
Continuous voltage/current variations |
Audio pre‑amp |
| Mixed‑Signal |
Combines analog & digital blocks |
ADC/DAC front‑end |
6. Common Circuit Topologies
- Series – Same current flows, voltages add.
Use: Voltage dividers, string LEDs.
- Parallel – Same voltage across branches, currents add.
Use: Power distribution, load sharing.
- Voltage Divider – Two resistors in series provide a selectable output voltage:
[
V_{out}=V_{in}\frac{R_2}{R_1+R_2}
]
- Current Mirror – Paired transistors copy a reference current to