# Analog Filter & Bode > Design passive RC/RLC and Sallen-Key filters up to 2nd order: pick topology and values, read cutoff, Q and the Bode plot — or start from frequency and get the components. Practice: elettronica Status: Proto v0.1 Tag: Filtri, RC, RLC, Sallen-Key, Bode Method, assumptions and limits: Page: --- Tool for analog filters up to second order. Analysis mode: enter R/L/C and topology, get cutoff frequency, Q factor and an interactive Bode plot (magnitude and phase). Design mode: start from the cutoff frequency (and Q for 2nd order) and get component values with the nearest E-series part. Includes Sallen-Key active synthesis with an op-amp. This file is a **descriptor**, not the tool's documentation: it says what the tool computes and by what method, in summary. Formulas, assumptions, validity conditions and limits are in the wiki linked above. The tool runs in the browser at the page given.