Electronics

1. Basic Components & Concepts

  • Atom: Basic unit of matter (Proton+, Neutron, Electron-).
  • Current (I): Flow of electric charge.
    • Formula: \( I = \frac{Q}{t} \)
    • Unit: Ampere (A)
  • Voltage (V) or EMF: Potential difference/Electrical pressure.
    • Unit: Volt (V)
  • Resistance (R): Opposition to current flow.
    • Formula: \( R = \frac{V}{I} \)
    • Unit: Ohm (Ω)
  • Conductance (G): Reciprocal of resistance. \( G = \frac{1}{R} \). Unit: Siemens (S).

2. Ohm’s Law & Power

  • Ohm’s Law: \( V = I \times R \)
  • Electrical Power (P): Rate of doing work.
    • Formula: \( P = V \times I = I^2 R = \frac{V^2}{R} \)
    • Unit: Watt (W)
  • Electrical Energy (E): \( E = P \times t \). Unit: Joule (J) or kWh.

3. Circuit Elements

  • Resistor: Opposes current. Color codes used for value.
  • Capacitor (C): Stores energy in an electric field.
    • Formula: \( C = \frac{Q}{V} \)
    • Unit: Farad (F)
  • Inductor (L): Stores energy in a magnetic field. Unit: Henry (H).

4. Series and Parallel Circuits

  • Series Circuit:
    • Current (I): Same throughout. \( I_{total} = I_1 = I_2 = … \)
    • Voltage (V): Divides. \( V_{total} = V_1 + V_2 + … \)
    • Resistance (R): Adds up. \( R_{total} = R_1 + R_2 + … \)
  • Parallel Circuit:
    • Current (I): Divides. \( I_{total} = I_1 + I_2 + … \)
    • Voltage (V): Same across all. \( V_{total} = V_1 = V_2 = … \)
    • Resistance (R): Reciprocal sum. \( \frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + … \)

5. Semiconductors

  • Conductor: e.g., Copper. Low resistance.
  • Insulator: e.g., Rubber. Very high resistance.
  • Semiconductor: e.g., Silicon (Si), Germanium (Ge). Conductivity between conductor and insulator.
  • Doping: Adding impurities to a semiconductor to change its properties.
    • N-type: Doped with Pentavalent atoms (e.g., Phosphorus). Majority carriers are electrons.
    • P-type: Doped with Trivalent atoms (e.g., Boron). Majority carriers are holes.
  • PN Junction: Formed by joining P-type and N-type semiconductors. Forms a Depletion Region and acts as a diode.

6. Diodes

  • A two-terminal device that allows current to flow primarily in one direction (Forward Bias) and blocks it in the opposite direction (Reverse Bias).
  • Rectifier: Converts AC to DC.
    • Half-Wave: Uses one diode. Conducts for half cycle.
    • Full-Wave: Uses two or four diodes (Bridge Rectifier). Conducts for full cycle.
  • LED (Light Emitting Diode): Emits light when forward biased.
  • Zener Diode: Special diode designed to operate in reverse breakdown region. Used for Voltage Regulation.

7. Transistors

  • A three-terminal semiconductor device used for amplification and switching.
  • Bipolar Junction Transistor (BJT):
    • Terminals: Emitter, Base, Collector.
    • Types: NPN and PNP.
    • Current Relationship: \( I_E = I_C + I_B \)
    • Current Gain (β): \( \beta = \frac{I_C}{I_B} \)
  • Modes of Operation: Cut-off (OFF), Active (Amplifier), Saturation (ON).
  • Acts as an Amplifier in the active region and as a Switch in cut-off and saturation regions.

8. Logic Gates

Basic building blocks of digital circuits. Process binary signals (0 – LOW, 1 – HIGH).

Gate Name Symbol Boolean Expression Truth Table (A, B, Y)
NOT Triangle + circle \( Y = \overline{A} \) (0,1), (1,0)
AND D-shaped \( Y = A \cdot B \) (0,0,0), (0,1,0), (1,0,0), (1,1,1)
OR Curved \( Y = A + B \) (0,0,0), (0,1,1), (1,0,1), (1,1,1)
NAND AND + circle \( Y = \overline{A \cdot B} \) Opposite of AND
NOR OR + circle \( Y = \overline{A + B} \) Opposite of OR
XOR OR + curved line \( Y = A \oplus B \) (0,0,0), (0,1,1), (1,0,1), (1,1,0)

9. Integrated Circuits (ICs)

  • A set of electronic circuits on a small flat piece of semiconductor material (chip).
  • Operational Amplifier (Op-Amp): High-gain voltage amplifier with differential inputs.
    • Golden Rules (Ideal Op-Amp):
      1. No current flows into the input terminals (\(I_+ = I_- = 0\)).
      2. The voltage at both input terminals is equal (\(V_+ = V_-\)).

10. Important Values & Units

  • Charge of electron (\(e\)): \( -1.6 \times 10^{-19} \) C
  • 1 eV (electronvolt): \( 1.6 \times 10^{-19} \) J
  • Speed of Light (\(c\)): \( 3 \times 10^8 \) m/s
  • 1 kWh: \( 3.6 \times 10^6 \) J

Summary of All Formulae

Current & Charge:
\( I = \frac{Q}{t} \)

Ohm’s Law & Power:
\( V = I R \)
\( P = V I = I^2 R = \frac{V^2}{R} \)
\( E = P \times t \)

Resistance (Series/Parallel):
Series: \( R_{total} = R_1 + R_2 + R_3 + … \)
Parallel: \( \frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + … \)

Capacitance:
\( C = \frac{Q}{V} \)

Transistor Currents:
\( I_E = I_C + I_B \)
\( \beta = \frac{I_C}{I_B} \)

Electronics