RL Filter Cutoff Calculator Formula
Understand the math behind the rl filter cutoff calculator. Each variable explained with a worked example.
Formulas Used
Cutoff Frequency
cutoff_hz = resistance / (2 * pi * l_h)Time Constant (L/R)
time_constant = l_h / resistance * 1000Variables
| Variable | Description | Default |
|---|---|---|
resistance | Resistance(Ω) | 1000 |
inductance_mh | Inductance(mH) | 10 |
l_h | Derived value= inductance_mh / 1000 | calculated |
How It Works
RL Filter Cutoff
f_c = R / (2 x pi x L)
Time constant tau = L/R. An RL low-pass passes DC and attenuates high frequencies.
Worked Example
R = 1k, L = 10 mH.
resistance = 1000inductance_mh = 10
- 01L = 0.01 H
- 02f_c = 1000 / (2pi x 0.01) = 15,915.5 Hz
- 03tau = 0.01 / 1000 = 0.01 ms
Frequently Asked Questions
RL vs RC filter?
Same rolloff rate (-20 dB/decade), but RL uses an inductor where RC uses a capacitor.
Why use RL over RC?
RL filters handle DC current better. Useful in power supply filtering.
Inductor disadvantages?
Inductors are larger, heavier, and more expensive than capacitors for most filter applications.
Ready to run the numbers?
Open RL Filter Cutoff Calculator