Resistor Programmable Audio Active Filter

Data Sheet

6/2014

Web Site “www.mix-sig.com”

© 2004-2014 Mixed Signal Integration 4

Mixed Signal Integration Corporation reserves the right to to change any product or specification without notice at any time. Mixed Signal Integration

products are not designed or authorized for use in life support systems. Mixed Signal Integration assumes no responsibility for errors in this docu-

ment.

SIMPLIFIED

If RFO1 = RFO2; RFO1=RFO2=1E9/Fo

RQ = Q * RFO2

LOWPASS

KLP = Lowpass Gain

RLP = RFO1/KLP ; RBP =

BANDPASS

KBP = Bandpass Gain

RBP = RQ/KBP; RLP =

HIGH PASS

Gain = 1

RLP =

NOTCH

RLP = RFO1 ; RBP =



ALL PASS

An External Op Amp Inverter is required

RLP = RFO1 ; RBP = RQ ; R1 = R2

LOW PASS ELLIPTIC

An External Resistor Divider is required on INHP

RLP = RFO1 ; RBP =



HIGHPASS ELLIPTIC



Choosing RFO

For applications where Q is > = 1, making RFO1 =

RFO2 will usually be a good simplification. For appli-

cations where Q is significantly less than one, the

maximum signal can be reduced. For example, if Q =

0.5, RFO2 = 100K and RQ = 50K, the signal at OUT1

will be twice OUT2 and will clip for large signals. By

using the general equations, it can be seen that one

solution to this problem would be to make RFO2 =

RQ = 50K and RFO1 = 200K.

R3

R4

INHP

INPUT

GND

_

+

R2

R1

RBP

GND

INBP

INPUT