Exact synthesis of SC filters using forward difference integrators

The authors outline an exact synthesis for switched-capacitor (SC) filters in the Z-domain. The method requires only a single type of building block: the parasitic-free forward difference integrator. It uses flowgraph simulation techniques to simulate cascade sections which realize the transmission zeros. These sections use transformer and gyrator simulations. It is pointed out that transformers and gyrators, though undesirable in classical passive realizations are simple and effective in simulation procedures. An example is presented of a fourth-order elliptic filter design. The SC realization is simulated using Monte Carlo techniques, and the results prove that the technique presented is insensitive to component variations. In addition, these structures are highly modular, a desirable feature for VLSI implementation.<>