4th Order Sallen Key Low Pass Filter Calculator
The 4th order Sallen Key low pass filter calculator is an essential tool for designing filters in audio, video, and signal processing applications. This calculator simplifies the process of creating low pass filters with a 4th order Sallen Key topology, ensuring optimal performance and minimal phase shift.
- Enter the desired cutoff frequency in Hertz.
- Enter the sample rate in Hertz.
- Enter the quality factor (Q).
- Click the “Calculate” button.
- View the results and filter coefficients below.
The 4th order Sallen Key low pass filter is designed using the following transfer function:
The calculator uses this transfer function to calculate the filter coefficients (a0, a1, a2, b1, b2) based on the provided cutoff frequency, sample rate, and quality factor.
Real-World Examples
Example 1: Design a 4th order Sallen Key low pass filter with a cutoff frequency of 1 kHz, a sample rate of 44.1 kHz, and a quality factor of 0.707.
Example 2: Design a 4th order Sallen Key low pass filter with a cutoff frequency of 20 Hz, a sample rate of 48 kHz, and a quality factor of 1.
Example 3: Design a 4th order Sallen Key low pass filter with a cutoff frequency of 10 kHz, a sample rate of 96 kHz, and a quality factor of 0.5.
Data & Statistics
| Coefficient | Value |
|---|---|
| a0 | 1.0000 |
| a1 | -1.8316 |
| a2 | 0.8234 |
| b1 | 1.8316 |
| b2 | -0.8234 |
| Coefficient | Value |
|---|---|
| a0 | 1.0000 |
| a1 | -1.9998 |
| a2 | 0.9999 |
| b1 | 1.9998 |
| b2 | -0.9999 |
Expert Tips
- Higher quality factors result in sharper cutoff frequencies but may introduce more phase shift.
- Increase the sample rate to improve filter performance and reduce aliasing.
- Consider using a higher order filter for more attenuation at higher frequencies.
What is the difference between a low pass and a high pass filter?
A low pass filter allows low-frequency signals to pass while attenuating high-frequency signals. A high pass filter does the opposite, allowing high-frequency signals to pass while attenuating low-frequency signals.
What is the quality factor (Q) in a filter?
The quality factor (Q) in a filter determines the sharpness of the filter’s response. A higher Q results in a sharper cutoff frequency.
What is aliasing and how can it be prevented?
Aliasing occurs when high-frequency signals are sampled at a rate lower than the Nyquist frequency. To prevent aliasing, ensure that the sample rate is at least twice the highest frequency of interest.