LC EMI Filter Design Calculator
Design an LC low-pass EMI filter for conducted emissions suppression — calculate inductance, capacitance, filter order, and attenuation at the stop band.
Formula
Reference: Williams & Taylor, "Electronic Filter Design Handbook" 4th ed.
How It Works
LC EMI filters are critical passive components used in electromagnetic compatibility (EMC) engineering to suppress high-frequency noise in electrical and electronic systems. These low-pass filters attenuate unwanted electromagnetic interference by using a combination of inductors (L) and capacitors (C) to create a frequency-dependent impedance network that reduces noise above a cutoff frequency.
Worked Example
Problem: Design an LC low-pass EMI filter with a 100 kHz cutoff frequency for a 50Ω system Solution: 1. Calculate inductor value: L = √2 * 50Ω / (2π * 100,000 Hz) = 35.4 µH 2. Calculate capacitor value: C = √2 / (50Ω * 2π * 100,000 Hz) = 16 nF 3. Verify cutoff frequency: fc = 1 / (2π * √(35.4µH * 16nF)) ≈ 100 kHz
Practical Tips
- ✓Always use components rated for the expected voltage and current
- ✓Consider using multiple filter stages for higher attenuation
- ✓Verify filter performance through actual measurements and EMC testing
Common Mistakes
- ✗Neglecting source and load impedance when calculating filter components
- ✗Ignoring parasitic capacitances and inductances in real-world implementations
- ✗Not considering the filter's insertion loss and power handling capabilities
Frequently Asked Questions
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