2.1 Basic Electrical Components

Understanding electrical symbols and components is essential before diving into PCB design.

Electrical Symbols

Familiarize yourself with common electrical symbols that represent various components on a schematic:

• Resistor:

  

• Capacitor:

  

• Inductor:

  

• Diode:

  

Basic Components

Resistors

Resistors limit the flow of electric current in a circuit. The relationship between voltage (V), current (I), and resistance (R) is described by Ohm's law: $V=RI$.

Capacitors

Capacitors store electrical energy temporarily and release it when needed. The formula for calculating charge (Q) is: $Q=CV$ where (C) is capacitance and (V) is voltage. It’s important to note that capacitors have an Equivalent Series Resistance (ESR) which affects their performance. This is given by $ESR = \frac{DF}{2 \pi f C}$ where DF is the dissipation factor.

Inductors

Inductors store energy in a magnetic field when electrical current passes through them. The voltage across an inductor is given by: $V = L \frac{dI}{dt}$ where (L) is inductance. Like capacitors, inductors also have an ESR.

Diodes

Diodes allow current to flow in one direction only, making them essential for rectification in power supply circuits.

Resistance Formulas

• Series Resistance: The total resistance in a series circuit is the sum of the individual resistances. $R_{total} = R_1 + R_2 + ... + R_n$

• Parallel Resistance: The total resistance in a parallel circuit is calculated using: $\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n}$

Capacitance Formulas

• Series Capacitance: The total capacitance in a series circuit is: $\frac{1}{C_{total}} = \frac{1}{C_1} + \frac{1}{C_2} + ... + \frac{1}{C_n}$

• Parallel Capacitance: The total capacitance in a parallel circuit is: $C_{total} = C_1 + C_2 + ... + C_n$

Equivalent Series Resistance (ESR)

• Capacitors and Inductors have an equivalent series resistance.
• This means:
  • Current is flowing through these components.
  • These components will dissipate power.
• $P=VI=I^2R=V^2/R$
• Each component has a maximum power dissipation.
• CHECK COMPONENT DATASHEETS

Summary