Bench Talk

Whether to prevent floating I/O pins on an MCU or to provide an interface between two circuits, pull-up resistors are a necessity. But what size resistor should you use?

As you get more advanced with your circuits you will start seeing circuit design patterns that may at first glance seem a bit weird. One such design pattern that can be confusing is the “open drain,” also called the “open collector” (when TTL circuits are involved). For the purpose of this blog we will use the term open collector, though the general principles apply to both technologies: Field Effect Transistors (FET) and Bipolar Junction Transistors (BJT).