Pi Networks the Smith Chart Way

[Ralph] is excited about impedance matching, and why not? It is important to match the source and load impedance to get the most power out of a circuit. He’s got …read more

Jun 27, 2025 - 06:20

[Ralph] is excited about impedance matching, and why not? It is important to match the source and load impedance to get the most power out of a circuit. He’s got a whole series of videos about it. The latest? Matching using a PI network and the venerable Smith Chart.

We like that he makes each video self-contained. It does mean if you watch them all, you get some review, but that’s not a bad thing, really. He also does a great job of outlining simple concepts, such as what a complex conjugate is, that you might have forgotten.

Smith charts almost seem magical, but they are really sort of an analog computer. The color of the line and even the direction of an arrow make a difference, and [Ralph] explains it all very simply.

The example circuit is simple with a 50 MHz signal and a mismatched source and load. Using the steps and watching the examples will make it straightforward, even if you’ve never used a Smith Chart before.

The red lines plot impedance, and the blue lines show conductance and succeptance. Once everything is plotted, you have to find a path between two points on the chart. That Smith was a clever guy.

We looked at part 1 of this series earlier this year, so there are five more to watch since then. If your test gear leaves off the sign of your imaginary component, the Smith Chart can work around that for you.