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- Thread starter SoaDMTGguy
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No buffering for the high pass filter means you have to include the effects of R source as well as R load.

If the source has a coupling capacitor, that should be included as well.

f = 1 / ( 2 x Pi x Reff x Ceff )

Where R effective = R source + ( R filter // R load )

and C effective = C filter x C source / ( C filter + C source )

If the source has a coupling capacitor, that should be included as well.

f = 1 / ( 2 x Pi x Reff x Ceff )

Where R effective = R source + ( R filter // R load )

and C effective = C filter x C source / ( C filter + C source )

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R source is the spec source output impedance.

C load is not likely to be significant unless f is high, and will complicate the calculation.

If R source is small, C load would in effect be in parallel with C filter.

So try to make C filter at least x20 larger than C load.

What cutoff frequency is this for?

C load is not likely to be significant unless f is high, and will complicate the calculation.

If R source is small, C load would in effect be in parallel with C filter.

So try to make C filter at least x20 larger than C load.

What cutoff frequency is this for?

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Does your source have an output coupling capacitor? Most commercial sources do.

It's likely C load will be very small and can be neglected, in a 100Hz filter.

Also need the R source and R load.

Since there are two variables and one equation, you have to choose one.

Try choosing R filter as R load /10, and see how C filter comes out.

A value for C filter around 0.1uF would be good, but may have to be larger due to R load value.

It's likely C load will be very small and can be neglected, in a 100Hz filter.

Also need the R source and R load.

Since there are two variables and one equation, you have to choose one.

Try choosing R filter as R load /10, and see how C filter comes out.

A value for C filter around 0.1uF would be good, but may have to be larger due to R load value.

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So a 10KΩ filter is a good load/source choice. For Xc=10KΩ@100Hz, C=0.16uF (R=~ 9K=10K//100K). For 11K (10k+1k) @100Hz, C=0.145uF. But you will not notice the difference if you just use standard cap like 0.15uF.R load is 110k. R source is 1k

Do I consider the capacitance for the filter containing R filter + R load? Do I add R source as well?

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