I have a doubt about passive filters in differential inputs.
In low pass configuration I found this thread (https://www.edaboard.com/threads/176766/) that tells me to use the RC constant as:
R = R1 + R2
C = C1
But, if I want a high pass do I need to use the same idea or something like this:
For best sensitivity , low offset and best common mode noise rejection use an Instrumentation Amp IC ( 3 opamps) and use the series RC to define your HPF cutoff (fc=1/(2pi RC) instead of R7 You can get these in 1 chip too. R6=R5 and gain = R5/R7 for 1st stage... R2/R1 for 2nd stage
Hi Godfreyl
What you said ? are you sure about that ? if yes see below , please :
Consider that you have two capacitors in series together , the equal capacitor will be c/2 if both are correspond together . thus : if C1=C2=C/2 .
Respect
Goldsmith
Yes, you calculated the time constant for given C values, while godfreyl calculated capacitor values to achieve a given cut off frequency. Both calculations are correct.
Iuri, I don't know what you are going to connect at the diff. high pass output - however, realize that there is no ground connection (no bias current for a possible next stage).
It depends on the signal content above 500Hz . It will appear as noise with frequency transformed. (Alias)
Anything at 1KHz and all harmonics will appear as DC.