# Introduction to Electronics/Lecture Schematics

• Lecture 5, Schematics
• Schematic diagrams and layout semantics

Back to: Topic:Electronic Engineering

## Basics

Schematics are used to describe electronic circuits to other people. For the most part they are a universal language that will cross most language barriers.

When viewing a schematic the first thing to know is when wires cross or when they are tied together.

 2 crossing wires that are not electrically tied together. 2 wires that cross and are electrically tied together.

## Resistors

Resistor denotes any element of a circuit thats main function is resistance or ohms. There are 2 styles of resistor symbols UK and US. The UK style is a simple rectangle and the US style is a upside down VV.

When using the US style its ideal to denote the power requirement/dissipated power in text as shown in the table.

When using the UK style you can use either the power denoting or common but its best for the common symbole to denote power dissipated to prevent someone from guessing, more info is generally better.

Resistor symbols and their powers
All resistors are shown with the example of 150k ohms. The common resistors are shown with a example of 4Watts.
UK US
Common
r1 150k 4W

r1 150k 4W
1/20th watt
r1 150k

r1 150k .05W
1/8th watt
r1 150k

r1 150k 1/8W
1/4th watt
r1 150k

r1 150k 1/4W
1/2 watt
r1 150k

r1 150k 1/2W
1 watt
r1 150k

r1 150k 1W
2 watts
r1 150k

r1 150k 2W
5 watts
r1 150k

r1 150k 5W

## Capacitors

Capacitors generally are always some form of symbol showing 2 plates parallel to each other. The old capacitor symbol most likely dates back to the fact that at first scientists were unsure if the electrons are being stored in the dielectric between the plates or in the plates themselves. [factual?] Later it has been decided that the dielectric simply acts as a insulator and electrons are stored on the metal plates of a capacitor.

Capacitor symbols
unpolarized polarized
• current standard recommended
• has both polarization indication curve and + symbol
• offers more info than usually needed on unpolarized caps as the curve points to negative which is good.

• older standard usage discouraged no curved line
• only the + symbol for identifying polarity and no polarity indication on unpolarized caps.

• old cap symbols sometimes still seen

• less common capacitors

## MOSFET

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