(4st order, 24 dB/octave, Highpass)
C=4.7n-10nF
<math>Ra=Rc=\frac {1}{\sqrt{2\pi} \times Fc \times C}</math>
<math>Rb=Rd=2 \times Ra</math>
Units: Rx [Ω], C [F], Fc [Hz]
