Kirchhoff’s Circuit Laws

In one of my first circuits courses, the professor’s favorite words of advice were to “keep calm and remember KCL, KVL, and Ohm’s law.” With these three concepts, just about any electrical circuit can be analyzed and understood. Granted, things get a little more complicated when you add concepts like inductance and capacitance, but KCL, KVL, and Ohm’s law form the foundation of all circuit analysis. Brandon mentioned Ohm’s law in his blog post on how to choose a resistor for your design, so I will only be discussing KCL and KVL.

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How to Choose a Resistor for Your Design

Take a look at a circuit board and chances are you’re going to find a resistor or two. Most boards today use surface-mount device (SMD) technology, so the components are almost too small to see sometimes, but they are on there, I promise. How do engineers decide which resistors to use in the design? Sometimes it depends on how you want that portion of the circuit to perform, as in the case of an op-amp. Other times it’s to prevent too much current from passing through a given point in a circuit, which is why they are often called current-limiting resistors. Maybe you want a simple way to divide the voltage or current. The reality is that there are numerous ways to use resistors, and oftentimes, the defining the resistor value is up to you.

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