Active Filter Design

Lowpass Filter


C2 = 4 Q2 C1
R = 1 / ( 4π Fο Q C1 )

Enter Values: C1, Fο, and Q

uF kHz

Derived Component Values

uF kΩ

Highpass Filter

R1 = 1 / ( 4π Fο Q C)
R2 = 4 Q2 R1

Enter Values: C, Fο, and Q

uF kHz

Derived Component Values:

kΩ kΩ

Bandpass Filter

R = Q / ( π Fο C )
REQ = R / ( 4 Q2 )
AV = 2 Q2
AVR = AVT / AV
RB = REQ / AVR
RA = ( RB * AVR ) / ( 1 - AVR )

Enter Values: C, Fο, Q, and AVT:

uF kHz Total Circuit Gain (inverting)

Derived Component Values:

kΩ kΩ kΩ kΩ

Lowpass Filter with Gain

R = 1 / ( 2π C Fο)
Ry = Rx ( AVT - 1 )

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

if ( AVT ≦ 2.0)
Q_Limit = Infinity

Select Q < Q_Limit

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

Enter Values: Fο, C, AVT, Rx
Compute: Q_Limit

kHz uF kΩ

Enter Value for Q, where Q < Q_Limit

Derived Component Values

kΩ uF kΩ kΩ

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

Gain (k < 0) (0 < Q < 1) kHz uF

Compute: R, m, mR, Rk, Cm

kΩ kΩ kΩ uF

The High Order Filter Table (2015)


Frequency & Time Response

Butterworth

Bessel


Component Values