RC Filter Calculator
A single resistor and capacitor is often all you need to knock down noise on a sense line or set a corner frequency ahead of an ADC input. This calculator solves the first-order RC low-pass or high-pass corner frequency in either direction — pick R and C to hit a target cutoff, or check what corner an existing R/C pair on a board actually produces.
RC Filter
First-order low-pass / high-pass corner frequency
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Topology
Solve for
Corner frequency
1.59 kHz
Capacitance
100 nF
Time constant τ
100 µs
10–90% rise time
220 µs
Roll-off
−20 dB/dec above fc
For anti-alias filtering, place the corner at roughly 1/10 of the sample rate. For an ADC driver, τ should be under about 1/8 of the acquisition window so the sampling cap settles.