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RC Filter Calculator

Determine the cutoff frequency (-3dB point) for passive Low-Pass and High-Pass circuits.

Filter Parameters

Low-Pass Filter
High-Pass Filter

Frequency Response

0 dB -3 dB 159.15 Hz
Cutoff Frequency (ƒc) 159.15 Hz

Understanding RC Filters

The Concept

An RC circuit consists of a Resistor and a Capacitor. Because capacitors react differently to signals depending on their frequency (acting like a block to DC and a short circuit to high-frequency AC), we can use them to filter out unwanted noise from our signals.

  • Low-Pass Filter: Allows low frequencies to pass through but blocks high frequencies. Excellent for removing high-frequency noise from analog sensor readings.
  • High-Pass Filter: Allows high frequencies to pass and blocks low frequencies. Often used in audio circuits to remove DC offset or low rumble.

The Math

The crucial characteristic of a filter is its Cutoff Frequency (ƒc), also known as the -3dB point. This is the exact frequency where the output signal loses half its power. It is calculated identically for both Low and High pass configurations:

ƒc = 1 / (2 × π × R × C)