1. What is Low Pass Filter Cutoff Frequency?

The cutoff frequency (f_c) of a low pass filter is the frequency at which the output signal is attenuated to -3dB (about 70.7%) of the input signal. It determines the point where higher frequencies begin to be significantly reduced.

2. How Does the Calculator Work?

The calculator uses the standard RC low pass filter formula:

Where:

• \( f_c \) — Cutoff frequency in Hertz (Hz)
• \( R \) — Resistance in Ohms (Ω)
• \( C \) — Capacitance in Farads (F)
• \( \pi \) — Mathematical constant (~3.14159)

Explanation: The cutoff frequency is inversely proportional to both the resistance and capacitance values in the circuit.

3. Importance of Cutoff Frequency

Details: The cutoff frequency is crucial for designing filters that remove unwanted high-frequency noise while preserving the desired signal components in audio processing, communications, and signal conditioning applications.

4. Using the Calculator

Tips: Enter resistance in Ohms and capacitance in Farads (you can use scientific notation like 0.000001 for 1μF). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What happens at the cutoff frequency?
A: At f_c, the output voltage is 70.7% of the input voltage (-3dB point), and the phase shift is 45 degrees.

Q2: How does changing R or C affect the cutoff?
A: Increasing either R or C lowers the cutoff frequency, while decreasing them raises it.

Q3: What's the roll-off rate of a simple RC filter?
A: A first-order RC filter has a roll-off of 20dB per decade (6dB per octave) above the cutoff frequency.

Q4: Can I use this for active filters?
A: The basic formula applies to passive RC filters. Active filters may have different calculations depending on their design.

Q5: How accurate is this calculation?
A: The formula is theoretically exact, but real-world components have tolerances that affect the actual cutoff frequency.