Narrow Band Pass Filter Calculator
1st Order (6 dB per Octave) Narrow Band Pass
(diagram )
Formulas for first order only, calculate for L1 first, then C1.
L1 = Net Impedance / [(F2 - F1) x 6.283]
x 1,000 = L1 in (mHy)
Coil - L1
Millihenries (mHy)
C1 = 1 / (39.472 x [L1/1000] x [F1 x F2])
x 1,000,000 = C1 in (µfd)
Capacitor - C1
Microfarads (µfd)
2nd Order (12 dB per Octave) Narrow Band Pass
(diagram )
Formulas for second order only, calculate for C1 first, then L2, C2, L1.
L1 = 1 / (39.472 x C1 x [F1 x F2])
x 1,000 = L1 in (mHy)
Coil - L1
Millihenries (mHy)
C1 = .707 / (Net Impedance x 6.283 x [F2 - F1])
x 1,000,000 = C1 in (µfd)
Capacitor - C1
Microfarads (µfd)
L2 = 1 / (C1 x [6.283 x (F2 - F1)]2 )
x 1,000 = L2 in (mHy)
Coil - L2
Millihenries (mHy)
C2 = 1 / (39.472 x L2 x [F1 x F2])
x 1,000,000 = C2 in (µfd)
Capacitor - C2
Microfarads (µfd)
3rd Order (18 dB per Octave) Narrow Band Pass
(diagram )
Formulas for third order only, calaculate for L3 first, then C2, C3, L2, L1, C1.
L1 = 1 / (.499849 x [6.283 x
(F2 - F1)]2 x C2) x 1,000 = L1 in (mHy)
Coil - L1
Millihenries (mHy)
C1 = 1 / (39.472 x [F1 x F2] x L1)
x 1,000,000 = C1 in (µfd)
Capacitor - C1
Microfarads (µfd)
L2 = 1 / (39.472 x [F1 x F2] x C2)
x 1,000 = L2 in (mHy)
Coil - L2
Millihenries (mHy)
C2 = 1 / (1.4884 x [6.283 x
(F1 - F2)]2 x L3 x 1,000,000 = C2 in (µfd)
Capacitor - C2
Microfarads (µfd)
L3 = (.5 x Net Impedance) /
(6.283 x [F2 - F1]) x 1,000 = L3 in (mHy)
Coil - L3
Millihenries (mHy)
C3 = 1 / (39.472 x [F1 x F2] x L3)
x 1,000,000 = C3 in (µfd)
Capacitor - C3
Microfarads (µfd)