Capacitor Frequency Calculator

This tool calculates the cut-off frequency of a capacitor, within the context of a circuit, such as in an RC (resistor-capacitor) filter.

Calculator

Formula

fcā€‹ = 1/(2Ļ€*R*C)ā€‹

  • fcā€‹ is the cutoff frequency in Hertz (Hz)
  • R is the resistance in Ohms (Ī©)
  • C is the capacitance in Farads (F)
  • Ļ€ is the mathematical constant Pi (approximately 3.14159)

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Example Calculation

The cutoff frequency for a RC network with R = 10 kĪ© and C = 1 nF is 15.92 kHz. For a low pass filter, signals at frequencies above this value will be attenuated. For a high pass filter, signal frequencies below this value will be attenuated.

A schematic drawing of a simple low pass filter is shown below

RC low pass Filter Schematic

And here is the frequency response

Butterworth response

The calculator to find the 3 dB point shown above for R and C values.

Background

One of the most fundamental characteristics to calculate is the cutoff frequency (fc) of an RC filter. This is the frequency value at which the output signal drops to 70.7% (or -3 dB) of its input signal level for a low-pass or high-pass filter.

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