Switching sequence effects in switched-current filters

Problems are discussed which appear in some structures proposed for switched-current filters when changes in the C_gs capacitances of MOS transistors due to changes in the operating region are taken into account, and when it is not assumed that the transition from one switching phase to another is instantaneous. It is demonstrated that circuits based on the low sensitivity `second generation´ integrators, or on single transistor current memories, cannot be treated as simple two-phase circuits. These circuits actually require a four-phase switching system