RLC Notch Filter
An RLC notch filter rejects a narrow band by providing a low-impedance shunt path at its tuned frequency. In this example, the inductor and capacitor are in series from the signal node to ground. At their resonant frequency the branch draws signal away from the output load; above and below that point its impedance rises. The input resistor limits loading and helps define the depth and width of the notch. This is a useful diagram for explaining unwanted tone suppression and interference rejection. Real notch depth depends on component Q, tolerances, source impedance, and load impedance, so prototype or simulate a design before relying on the ideal response.
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Scenario
Tuned shunt notch filter
Key decisions
- Notch branch: Put a series L-C path from signal to ground.
- Isolation: Use a series resistor ahead of the output.
- Load: Include the next-stage input resistance.
When to reuse this
Use to illustrate a tuned branch that attenuates one narrow frequency region.
Frequently asked questions
What does a notch filter remove?
Why is the L-C branch in series?
What limits notch depth?
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