RC High/Low Pass Filter Calculator
Calculate cutoff frequency for RC high-pass and low-pass filters.
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Select the filter type (high-pass or low-pass), then enter the resistance in ohms and capacitance in farads. The calculator computes the cutoff frequency and time constant.
About RC High/Low Pass Filter
RC filters are fundamental building blocks in electronics. A low-pass filter passes signals with frequencies below the cutoff frequency while attenuating higher frequencies. A high-pass filter does the reverse. The cutoff frequency for both types is fc = 1/(2 x pi x RC), where the output drops to -3 dB. RC filters are used in audio processing, power supply smoothing, signal conditioning, and communication systems.
Frequently Asked Questions
What is a cutoff frequency?
The cutoff frequency is the frequency at which the output signal power drops to half (-3 dB) of the input. Below this frequency, a low-pass filter passes signals; above it, signals are attenuated.
What is the difference between high-pass and low-pass filters?
A low-pass filter allows frequencies below the cutoff to pass and attenuates higher frequencies. A high-pass filter does the opposite, passing higher frequencies and blocking lower ones.
What is the time constant?
The time constant (tau = RC) is the time it takes for the circuit to charge or discharge to about 63.2% of its final value. It equals the reciprocal of the angular cutoff frequency.