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For Educators · EMI Filter

EMI Filter for a phase-locked loop

Built for educators teaching it to a class. Drop a live demo into a lecture or assign it as a shareable link — no lab installs. Simulate a phase-locked loop live below — adjust the inputs and watch it respond, right in your browser.

Filter Designer

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Analog Filter DesignerLive

RC & RLC frequency response

Controls

Presets

Resistance R (Ω)

Capacitance C (nF)

Passive filters shape a signal's frequency content with resistors, capacitors, and inductors. An RC low-pass or high-pass has a cutoff at 1/(2πRC) where the response drops 3 dB; an RLC bandpass resonates at 1/(2π√(LC)) with sharpness set by its quality factor Q.

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Data Inspector

Cutoff fc1.6 kHz

Resonance f₀5.0 kHz

Quality factor Q0.32

Governing equation

∣ H (f) ∣ = \frac{1}{1 + ( f /1592 ) ^{2}}

Reading this result: Low-pass: signals below the 1.6 kHz corner pass, above it they roll off at 20 dB/decade, and the response is exactly 3 dB down right at the corner.

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Bode Plot

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Bode Plot (2nd-Order System)Live

frequency response

Controls

Presets

Natural frequency (Hz)

Damping ratio ζ

A Bode plot shows how a system responds across frequency: gain in decibels on top, phase shift below. This second-order low-pass passes low frequencies and rolls off at −40 dB/decade above its natural frequency. Low damping produces a resonant peak; high damping smooths it away.

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Data Inspector

Natural freq1,000 Hz

Damping ζ0.30

Resonant peak+4.8 dB

Roll-off−40 dB/dec

Governing equation

H (s) = \frac{ω _{n}^{2}}{s ^{2} + 2 ζ ω _{n} s + ω _{n}^{2}} = \frac{6 , 28 3 ^{2}}{s ^{2} + 3770 s + 6 , 28 3 ^{2}}

Reading this result: Low damping ζ=0.30 produces a sharp +4.8 dB resonant peak just below fn — great for selectivity, but it rings in the time domain.

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Frequently asked questions

Is this good for educators?: Yes — this version of "EMI Filter for a phase-locked loop" is framed for educators teaching it to a class. Drop a live demo into a lecture or assign it as a shareable link — no lab installs.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.