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Active Low Pass Filter

Sallen-Key topology, gain, second order response.

Mohith N
Updated: 19 March 2026
6 min read

Active Low Pass Filter

Test your knowledge of Sallen-Key LPF topology, second-order response characteristics, and Butterworth design conditions.

Question 1 of 3

Q1.A second-order Sallen-Key LPF has the transfer function H(s) = wn^2 / (s^2 + (wn/Q)*s + wn^2). For a Butterworth response (maximally flat passband), the Q factor must be: