RC Filter Calculator
Calculate the cutoff frequency (fc) of a resistor-capacitor (RC) filter.
RC Filter Parameters
RC Filter Cutoff Frequency Formula
The cutoff frequency (fc) for an RC filter is calculated using the formula:
Where:
- fc is the cutoff frequency in Hertz (Hz)
- R is the resistance in Ohms (Ω)
- C is the capacitance in Farads (F)
Common Resistor and Capacitor Values
| Component Type | Common Values |
|---|---|
| Resistors (Ohms) | 10, 22, 47, 100, 220, 470, 1k, 2.2k, 4.7k, 10k, 22k, 47k, 100k, 220k, 470k, 1M |
| Capacitors (nF) | 1, 2.2, 4.7, 10, 22, 47, 100, 220, 470 |
| Capacitors (μF) | 0.001, 0.01, 0.1, 0.22, 0.47, 1, 2.2, 4.7, 10, 22, 47, 100, 220, 470, 1000 |
Typical Cutoff Frequencies for Applications
| Application | Typical Cutoff Frequency Range |
|---|---|
| Audio Filters (Low-Pass) | 20 Hz - 20 kHz |
| Audio Filters (High-Pass) | 20 Hz - 20 kHz |
| Power Supply Filtering | 100 Hz - 1 kHz |
| Sensor Signal Conditioning | 1 Hz - 10 kHz |
| RF Filters | > 1 MHz |
Frequently Asked Questions
What is an RC filter?
An RC filter is an electrical circuit consisting of a resistor and a capacitor. It is commonly used to filter out unwanted frequencies from an electrical signal. Depending on the configuration, it can act as a low-pass filter (allowing low frequencies to pass) or a high-pass filter (allowing high frequencies to pass).
What is cutoff frequency?
The cutoff frequency (also known as the -3dB frequency or half-power frequency) is the frequency at which the output power of the filter is half of the input power, or the output voltage is 1/√2 (approximately 70.7%) of the input voltage. It marks the boundary between the frequencies that are passed and those that are attenuated by the filter.
How do I choose R and C values?
The choice of R and C values depends on the desired cutoff frequency and the application. Generally, you select standard resistor and capacitor values that are readily available and combine them to achieve the desired cutoff frequency. Consider factors like power dissipation for the resistor and voltage rating for the capacitor.