Logic Families

A “logic family” is a standardized way of creating logic gates. Consider that there are many different ways to make a NAND gate. For example: in lab, we used one configuration of transistors and resistors, but we could just as easily have attached our “NOT” gate to the output of our AND gate and achieved the same result with a different configuration.

It is important to know what configuration the pre-made ICs you are using are set to, so that you know how to treat floating pins, where you expect currents to flow, and what precautions to take, etc. This is why the standardized logic families were created. We will talk about two of the most common logic families, starting with TTL (Transistor-Transistor Logic) and then the more widely-used CMOS (Complementary Metal Oxide Semiconductor).