Basic electronics

Objectives:

Basic Electronics β€” Notes with Diagrams

Basic Electronics β€” Notes with Diagrams (HTML)

A single-file, printable reference with inline SVG diagrams β€” ideal for students and hobbyists.

1. Quick Overview

Electronics studies how devices control electron flow to process signals and energy. This document explains basic quantities, common components, circuit types and examples β€” accompanied by diagrams you can zoom and print.

2. Fundamental Quantities & Formulas

QuantitySymbolUnit
VoltageVVolt (V)
CurrentIAmpere (A)
ResistanceROhm (Ξ©)
CapacitanceCFarad (F)
InductanceLHenry (H)

Key formulas: V = I Γ— R β€” Ohm's Law. P = V Γ— I β€” Power.

3. Passive Components (Diagrams)

Resistor (R) Capacitor (C) Inductor (L)

Resistors limit current. Capacitors store charge (useful for timing & filtering). Inductors store energy in magnetic fields (used in filters and power supplies).

4. Active Components (Diagrams)

PN Junction Diode (-> only forward conducts) LED (Light Emitting Diode) β€” needs series resistor NPN transistor (B β€” base, C β€” collector, E β€” emitter)

Diodes allow current one way. Transistors act as amplifiers or switches (BJT: base controls collector-emitter current).

5. Circuit Topologies (Series & Parallel)

Series circuit β€” same current flows through each resistor Parallel circuit β€” nodes share same voltage

6. Practical Example β€” LED + Resistor

To light an LED from a DC source you must add a series resistor to limit current. Example calculation:

Given: V_supply = 9V, V_LED β‰ˆ 2V, desired I_LED = 20mA
R = (V_supply - V_LED) / I_LED = (9 - 2) / 0.02 = 350Ξ© β†’ choose 360Ξ© standard value
Battery 9V R = 360Ξ©

7. Power Supplies & Rectifiers

The common chain: Transformer (optional) β†’ Rectifier β†’ Filter β†’ Regulator.

Full-wave Bridge Rectifier (AC in β†’ DC out) DC+ DC-

Use filter capacitor after rectifier to smooth DC, and a regulator (e.g., 7805) to keep voltage steady.

8. Signals, Frequency & Reactance

AC signals vary with time. Frequency f in Hz determines reactance: X_C = 1/(2Ο€fC) and X_L = 2Ο€fL.

AC Sinewave (varying) DC (constant)

9. Digital Logic β€” Gates (SVG)

AND OR NOT (Inverter)

Combine gates to build adders, counters, and memory elements. Digital circuits use TTL or CMOS families β€” but microcontrollers now perform most logic tasks in modern projects.

10. Tools & Safety

  • Multimeter β€” measure voltage, current, resistance.
  • Breadboard β€” assemble circuits without solder.
  • Soldering iron β€” permanent connections (use ventilation).
  • Oscilloscope β€” view waveforms.

Safety tips: Always power down before changing wiring, discharge large capacitors, use eye protection, and double-check polarities (especially electrolytic capacitors and diodes).

11. Small Project Ideas

  1. LED flasher (using 555 timer or microcontroller)
  2. Light-sensitive night lamp (LDR + transistor)
  3. Simple amplifier for a phone audio
  4. Full-wave rectifier + regulator power supply
  5. Digital counter using 74-series ICs or Arduino

12. Printable Reference (Cheat Sheet)

Ohm's law: V = I Γ— R
Power: P = V Γ— I
Capacitive reactance: Xc = 1/(2Ο€fC)
Inductive reactance: Xl = 2Ο€fL
Series R: R_total = R1 + R2
Parallel R: 1/R_total = 1/R1 + 1/R2
KCL: Ξ£I_in = Ξ£I_out
KVL: Ξ£V_around_loop = 0

Common components: R, C, L, D, LED, BJT, MOSFET, IC, Transformer

Tools: Multimeter, Breadboard, Soldering iron, Oscilloscope

How to download the HTML file

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Reference Book: N/A

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