The basic symbols of resistors, capacitors, and other components are pretty easy to remember and you can find them listed in many different places. The real concern comes with how to work with these symbols in your schematic in order to provide the most useful information. We’ll take a look at some of the basics of schematic diagram symbols here and how you can best utilise them in your designs.
What is Symbols , shapes, or Components
Symbols are drawn to be pretty simple while conveying the information of what they are and what they do. For instance, a capacitor symbol is two vertical lines side-by-side with horizontal lines going off the sides for the pins. A resistor is a set of nine diagonal lines connected together with horizontal lines going off the sides for pins. Logic gates are represented by either a rectangle with a rounded end, or a triangle, and will have multiple lines going off the sides for pins. Logic gates with pins that have a small bubble on the output pin lines indicate that its function is negated.
There are many, many schematic symbols and there are also many different ways that they are represented depending on the style and needs of the user. One company may encourage you to rotate a symbol on a schematic sheet while another company may not. The key is to learn what is the standard practice at your company and to stick with that.
Another important part of understanding the basics of schematic diagram symbols is to know the difference between symbols, shapes, and components. A symbol is the logical representation of an electronic component on the schematic sheet. Although shape is sometimes used to reference the appearance of a symbol, it is most often used to describe the physical shape of an electronic component in the PCB layout. A component is the physical part used on the circuit board. However, it is also common practice for both schematic users and PCB layout engineers to refer to their symbols and shapes as components. Yes, this can be a bit confusing if you aren’t used to it, but after some repetition, it will begin to make sense. As they say: context is everything.
How Your PCB Design Tools Can Help
The schematic capture tools in your PCB design system typically have advance drafting features to help you create the schematic symbols that you need. You will have the ability to draw straight lines for capacitors, diagonal lines for resistors, curved lines for logic gates, and many other primitive drawing shapes as well.
Usually, the placement of pins in a schematic symbol is an automated function of the tools so that the pins will carry intelligent information with them. This information is used by the PCB layout tools to identify the pin, as well as by the simulation tools. Schematic symbols can also usually be loaded with other intelligent information such as a unique reference designator, footprint, a part number, tolerances, values, and whatever other information is required for their function. Complete information is stored in this symbol and transferred to layout in a net-list file.