sir,
Iam very new to the concept of filter designing.I want to design a high pass filter (butterworth) with op-amp .I need a cut-off frequency of .03hz.how should I proceed?

The simplest configuration for a Butterworth alignment is a Sallen-Key arrangement.Do you want a single pole(6dB/octave) or double pole(12dB/octave) filter?
A double pole SallenKey would look like this :


For a butterworth alignment C1=C2 and R2=2xR1.
The corner frequency is determined by R1 and C1.
For calculating component values first settle on the capacitor value...say 47uF.
Then
R1=0.707/(2*pi*F*C1)
In your case
R1 = 0.707/(2 * 3.14 * 0.03 * 0.000047)
R1=80K
Thus R2=160K
C1=C2=47uF

thanks shashi, very useful info. Hope Priya got the answer :-)

thanx a lot shashi sir,i just want to know if I choose a single pole filterhow will the circuit look like?
sir also provide me the values of capacitors resistors for the respective circuit

hello priya123,

can we know where you are using this filter- i mean which circuit/application


Arun

A single pole filter will have only a single capacitor-resistor pair. Like this ..



The formula is..
F = 1/(2*pi*R*C)

For F = 0.03Hz and C = 57uF(47uF and 10uF in parallel),R will come to ~93K.

Why have you chosen such a low cutoff? Some medical equipment?

hello sir,
u are absolutely right ,actually I am trying to design a medical ECG monitoring circuit using instrumentation amplifier ad620a,some filter with a low cut-off,just one more query sir,please tell me how to design a protection/isolation circuit to prevent current leakage.
thanking u.

hi,

for medical application u want to know more abt the signal processing, first wat is the range of frequency you going to monitor.. for u r using protection circuits (isolation)