ELECTRONICS
Sallen-Key Second-Order Butterworth Low-Pass Filter
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CASE ANALYSIS
Scenario
A design engineer needs a second-order Butterworth low-pass filter to attenuate high-frequency noise while maintaining a maximally flat passband response.
Key decisions
- Use unity-gain Sallen-Key topology for a 2-pole Butterworth response
- Select R1=R2=10k and C1=10nF, C2=4.7nF for Q≈0.73
- Power the op amp with ±12V and decouple both rails with 100nF capacitors
When to reuse this
For audio, sensor, or instrumentation signal conditioning requiring a 2-pole 40 dB/decade rolloff with buffered output.
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