Distortion analysis of the alternative doubly-terminated ladder fully-differential Gm-C filters

In this paper, distortion analysis of the alternative doubly-terminated ladder fully-differential Gm-C filters, which are designed such that the differential-mode voltage experienced by each transconductor is minimized, is developed. The closed-form matrix solutions of the distortion of these filters are derived and simple in-band distortion equations are also given. It was found that the third-harmonic component of the alternative ladder Gm-C filter is eight times lower than that of the conventional Gm-C filter. These mathematical results supplement the intuitive understanding of the low-distortion nature of the alternative Gm-C structure.