Impedance & Reactance
Unlike pure resistors, the impedance of Inductors and Capacitors changes based on the frequency of the signal passing through them. This frequency-dependent resistance is called Reactance ($X$).
The Inductor (L)
Inductors resist changes in current. At very low frequencies (DC), an inductor acts like a piece of wire (short circuit). As frequency increases, it becomes harder for the current to change direction, so the impedance increases linearly.
The Capacitor (C)
Capacitors resist changes in voltage. At very low frequencies (DC), a capacitor blocks current completely (open circuit). As frequency increases, the capacitor charges and discharges fast enough that it appears as a short circuit.
Component Setup
Adjusting Inductance (1 to 100 nH)
Visible Traces
*Traces auto-update the rectangular chart below.
Impedance Magnitude |Z| (Ω)
S-Parameters (dB)
Smith Chart Visualizer
Generate an industry-standard .s2p file from your current settings and process it to render a high-fidelity Smith Chart.
Moving on the Smith Chart
If you requested a Smith Chart plot above, you'll notice how the traces hug the outer edge of the chart. The outer ring of the Smith Chart represents pure reactance (zero resistance).
- Inductors always plot on the top half of the Smith Chart. As frequency goes up, they travel clockwise toward the right side (Open Circuit / Infinite Impedance).
- Capacitors always plot on the bottom half of the Smith Chart. As frequency goes up, they travel clockwise toward the left side (Short Circuit / Zero Impedance).
Teaser: The Magic of Resonance
What happens if we put an Inductor and a Capacitor in the same circuit? Because $X_L$ goes up with frequency, and $X_C$ goes down, there is exactly one magical frequency where they cross. At this frequency, their reactances perfectly cancel each other out ($X_L - X_C = 0$). This is called Resonance, and it is the foundational concept behind all RF filters, matching networks, and antennas. We will build LC circuits in our next tutorial module!