Work out low pass filter cutoff instantly with clear inputs, formula shown and shareable results.
A single-pole RC low-pass filter has cutoff at 1/(2 pi RC), where output is 0.707 of input (-3 dB) and phase lag is 45 degrees. Above cutoff the response falls at 6 dB per octave, and the step response rise time is 2.2 RC.
RC low pass
fc = 1 / (2 pi R C); gain = 1 / sqrt(1 + (f/fc)^2); rise time = 2.2 R C
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
At fc the capacitive reactance equals the resistance, so the output is 1/sqrt(2) of the input — half the power, which is -3 dB.
Yes. The input impedance falls toward R at high frequency, so drive it from a low-impedance source and load it lightly.