Better yet is putting the power separate so you don’t clutter the signal flow. Better is when you break the part into its two halves. What is useless is the way the part comes in your CAD package. Showing the exact logic symbol is better than useless. Some semiconductor companies adopted that ANSI symbol for logic, obviously invented by linear minds that need to parse, as opposed the graphical minds of analog engineers ( Figure 2).įigure 2 The ANSI/IEEE logic symbol convention is disliked by many engineers and worse than useless. RP2 shows how a heterogeneous part can do this. Resistor pack RP1 is stupid, you don’t want to tangle up your schematic when the resistors should be at various places on the sheet. It has the six parts, as well as a 7th part that shows power and ground. Old guys like me don’t like colored backgrounds since six generations of a black-and-white copy turn the yellow into black and you can’t read anything. Here, the inputs are on the left and outputs are on the right. The pins are longer than they need to be. There are both inputs and outputs on both left and right. To this day, some companies draw their schematic symbol to mimic the pin-out of the part rather than the signal flow ( Figure 1 ). With semiconductor companies making so much money, and providing so much support, sometimes their tendency to be stuck inside the part makes the schematic flow disappear. I can scream at you, “Make it does difference what!?!” That syntactic, it kind of parses, but if I flow from left to right, “What difference does it make?” then you can understand it in a moment. This is not cast in concrete, but it’s pretty important if you want other engineers to be able to read your schematic at a glance. This flow requires inputs to the be on the left and top, while outputs are on the right and bottom. The tens of thousands of included symbols your CAD package brags about are simply a starting point for you to redraw them all. Make sure you have a package that makes symbol creation easy, since you will have to re-draw every single part, as well as create the new parts you use. Sometimes, the pre-packaged symbols in you CAD (computer aided design) package will work. It is important you make your schematic symbols understandable. In the comment section of my last article, there was some great discussion about drawing schematic symbols.