Active Filter Design

Lowpass Filter

C₂ = 4 Q² C1
R = 1 / ( 4π Fο Q C₁ )

Enter Values: C1, Fο, and Q

Highpass Filter

R₁ = 1 / ( 4π Fο Q C)
R₂ = 4 Q² R₁

Enter Values: C, Fο, and Q

Bandpass Filter

R = Q / ( π Fο C )
R_EQ = R / ( 4 Q² )
A_V = 2 Q²
A_VR = A_VT / A_V
R_B = R_EQ / A_VR
R_A = ( R_B * A_VR ) / ( 1 - A_VR )

Enter Values: C, Fο, Q, and A_VT:

Lowpass Filter with Gain

R = 1 / ( 2π C Fο)
R_y = R_x ( A_VT - 1 )

if ( A_VT < 2.0 )
Q_Limit = -1 / (A_VT - 2)

if ( A_VT ≥ 2.0)
Q_Limit = Infinity

Select Q < Q_Limit

Compute:
m = A_VT - 2 + ( 1 / Q )
Cm = C * m
Rm = R / m

Enter Values: Fο, C, A_VT, R_x
Compute: Q_Limit

Lowpass Filter with Gain (Inverting)

R = 1 / ( 2π C Fο)
m = (1/Q - 1) / (1 - k)
mR = m * R
Rk = R / -k
Cm = C / m

Enter Values: k, Q, Fο, C