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Bode Plotter

Plot frequency response (magnitude dB and phase °) for RC, RL, and RLC filter topologies

A Bode plot shows a filter's frequency response as magnitude (dB) and phase (°) against log-frequency. Together they fully characterise how any sinusoidal input is modified.

First-order RC low-pass

Cutoff frequency fc = 1/(2πRC). Below fc: 0 dB passband. At fc: −3 dB magnitude, −45° phase. Above fc: −20 dB/decade roll-off; phase asymptotes to −90°.

Second-order and higher

Each additional pole adds −20 dB/decade to roll-off and −90° to asymptotic phase. With complex poles an RLC resonance peak appears — height controlled by Q.