The two examples are from Alexander Sadiku's book but the graphics were made with multisim and pain. This is basic to what I will show in future publications about my research in the math degree applied to the area of ​​communications on the "advanced method of signal filtering by network synthesis using approximate polynomials". The polynomials with which both design, simulation and implementation works for both passive and active filters were: Butterworth, Chebishev Type I, Chebishev Type II, Legendre, Elipticos or Cauer, Laguerre, Hermite type I, Hermite Type II. I am currently working with the hyperbolic tangent function which is a pure lomito in the approach research for signal filtering.