Bandpass Filter Calculator Formula
Understand the math behind the bandpass filter calculator. Each variable explained with a worked example.
Formulas Used
Center Frequency
center_freq = 1 / (2 * pi * sqrt(l_h * c_f))Bandwidth (-3 dB)
bandwidth = resistance / (2 * pi * l_h)Quality Factor
q_factor = (1 / resistance) * sqrt(l_h / c_f)Variables
| Variable | Description | Default |
|---|---|---|
resistance | Resistance(Ω) | 50 |
inductance_mh | Inductance(mH) | 1 |
capacitance_nf | Capacitance(nF) | 10 |
l_h | Derived value= inductance_mh / 1000 | calculated |
c_f | Derived value= capacitance_nf / 1000000000 | calculated |
How It Works
RLC Bandpass Filter
f_center = 1 / (2pi x sqrt(LC))
Bandwidth = R / (2pi x L)
Q = f_center / Bandwidth
Higher Q = narrower pass band.
Worked Example
R=50, L=1 mH, C=10 nF.
resistance = 50inductance_mh = 1capacitance_nf = 10
- 01f_center = 1 / (2pi x sqrt(0.001 x 1e-8)) = 50,329 Hz
- 02BW = 50 / (2pi x 0.001) = 7,958 Hz
- 03Q = 50329 / 7958 = 6.33
Ready to run the numbers?
Open Bandpass Filter Calculator