xXGiuseppeXx
Newbie level 2
Hello all, I have always referred to this forum for any electrical questions but this is my first time posting; never thought I would have to!
Anyway my problem is this: I am playing around with passive, analog filters. I have been reading some theory here:
https://www.electronics-tutorials.ws/filter/filter_2.html
It all seems to make sense and I have made excel sheets and LTSpice simulations to solidify the theory.
However, the one thing that bugs me is the 2 pole RC filter. Towards the bottom I quote:
Q1:
Why a factor of 10 and how do they correspond to each other? I know it is to prevent loading from the filter stages but I am unsure why. In my LTSpice simulations, a factor of 100 is much better and is close to the -3dB point.
Q2:
In the next section, 2 pole, high pass, RC filters are discussed but they do not give a rule on which components to proportion to what. I have tried the rule and something similar to that in my Q1 but it simply does not work.
I figure if I can understand how they came to the factor in Q1, Q2 should be easier to understand and perhaps I can synthesize the factors (that is, if proportioning the filter's components is possible to prevent loading of each other).
Anyway my problem is this: I am playing around with passive, analog filters. I have been reading some theory here:
https://www.electronics-tutorials.ws/filter/filter_2.html
It all seems to make sense and I have made excel sheets and LTSpice simulations to solidify the theory.
However, the one thing that bugs me is the 2 pole RC filter. Towards the bottom I quote:
"In practice, cascading passive filters together to produce larger-order filters is difficult to implement accurately as the dynamic impedance of each filter order affects its neighboring network. However, to reduce the loading effect we can make the impedance of each following stage 10x the previous stage, so R2 = 10 x R1 and C2 = 1/10th C1."
Q1:
Why a factor of 10 and how do they correspond to each other? I know it is to prevent loading from the filter stages but I am unsure why. In my LTSpice simulations, a factor of 100 is much better and is close to the -3dB point.
Q2:
In the next section, 2 pole, high pass, RC filters are discussed but they do not give a rule on which components to proportion to what. I have tried the rule and something similar to that in my Q1 but it simply does not work.
I figure if I can understand how they came to the factor in Q1, Q2 should be easier to understand and perhaps I can synthesize the factors (that is, if proportioning the filter's components is possible to prevent loading of each other).