Active RC filter based on simulation of dissipative LC filters

A new class of active filters with all-pole lowpass response is proposed. The proposed circuits simulate the doubly terminated ladder filters realised by lossy capacitors and negatively dissipative inductors; that is, inductors accompanied with negative resistances. The number of required operational amplifiers is reduced to about two-thirds of that of the conventional leapfrog realisation. First, the synthesis method of an LC filter with lossy reactive elements to be simulated is described. Secondly, a method to simulate the LC filter is described. Finally, a fifth-order lowpass filter is designed and it is shown that the measured response agrees relatively well with the theoretical response. Furthermore, the element sensitivity is estimated by computer simulation and it is shown that the sensitivity of the proposed filter is slightly higher than that of the conventional leapfrog filter