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How to use a circuit diagram template.
- 01Select a second-order Butterworth low-pass filter template
Start from a pre-built Sallen-Key or multiple-feedback circuit to save time.
- 02Adjust component values
Change resistor and capacitor values to set your desired cutoff frequency and Q factor (typically 0.707 for Butterworth).
- 03Connect the signal path
Ensure the input, op-amp, and output are properly wired according to the chosen topology.
- 04Add annotations
Label nodes, component values, and the filter response to make the diagram self-explanatory.
- 05Export or share
Download as SVG, PNG, or share a live link to collaborate with your team.
Questions about circuit diagram templates
What is a second-order Butterworth low-pass filter?
A second-order Butterworth low-pass filter is an active filter that provides a maximally flat passband and a roll-off of -40 dB per decade above the cutoff frequency. It typically uses one operational amplifier and a few resistors and capacitors.
What is the difference between Sallen-Key and multiple-feedback topologies?
The Sallen-Key topology uses a non-inverting op-amp configuration and is simple with low component count, while the multiple-feedback topology uses an inverting configuration and can provide gain, often with better stopband performance.
How do I calculate component values for a second-order Butterworth filter?
For a second-order Butterworth response, set the quality factor Q to 0.707. You can choose a cutoff frequency and then calculate resistor and capacitor values using standard formulas or use a design tool like ChatDiagram to generate them automatically.
What is the cutoff frequency of a Butterworth filter?
The cutoff frequency is the point where the filter's response drops to -3 dB relative to the passband. For a second-order Butterworth low-pass filter, the response is -3 dB at the cutoff and continues to fall at -40 dB per decade.
Can I use a single-supply op-amp for a second-order Butterworth filter?
Yes, single-supply operation is possible by biasing the op-amp's non-inverting input to a mid-supply voltage and AC-coupling the input and output. The circuit diagrams on this page can be adapted for single-supply designs.