Contents 

1. What is Schematic
2. Schematic nets 
3. Naming the schematic nets 
4. What is PCB Layout 

1.Schematic 

The schematic is a drawing that defines the logical connection between components on a circuit board. It basically shows you how the components are electrically connected. A schematic contains a netlist which is a simple data structure that lists every connection in the design, as specified by the drawing. The below image shows an example of a schematic diagram.   

  An example of a PCB schematic diagram

The schematic diagram gives the following information: 

1. Components used 
2. Electrical connection between components pins 
3. Operation conditions such as voltage, current, tolerances 
4. Special instruction like placement of decoupling capacitors, crystals, resistors, inductors and etc. 

2.Schematic nets 

Schematic nets define how components are interconnected in a circuit. The line between the two interconnected components is called a net. 

Nets in a basic schematic diagram 

3.Naming the schematic nets 

In order to make the schematic diagram more legible, the nets are labeled with their names, rather than drawing lines to show the connectivity. The image below shows an example of a schematic diagram in which nets are labeled with their names. 

Schematic with labeled nets

4.PCB Layout 

The PCB layout shows the exact physical locations of every component on the PCB shows the physical wires(traces) that connect them together. An example of a PCB layout is shown below. 

An example of PCB layout 

What are the rules for drawing schematic diagrams  

Below are some of the best practices that should be following while drawing circuit diagrams: 

1. Electrical connection between the components are represented by lines. Lines that intersect with each other are not connected unless there is a node present at the point of intersection. 
2. It is always a good practice to have only 3 lines connected to at node. 
3. In complex circuits, it is recommended to design a name to nets. The nets with the same name are assumed to be connected. 
4. The pin numbers, polarity, values, and net names should be written horizontally. 
5. Place the inputs on the left and outputs on right. 
6. Design schematic sections in functional blocks. 
7. Always place pin numbers on the outside of the symbol graphic. 
8. Sheet connection symbols should always be placed on the extreme left edge or extreme left edge or extreme right edge of the page. 
9. Place the title block on the lower right corner of the first sheet. The title block should display the following information: 

            1.Title 

            2.Part number

            3.Revision (if any) 

Understanding the schematic diagram is very important for designers in order to design a successful PCB.