Continuous-time and switched capacitor monolithic filters based on current and charge simulation

The authors are concerned with high precision analogue filters for integrated circuit implementation that use current or charge variables to simulate low sensitivity LCR filters instead of voltages. The filters are regarded as interconnections of integrators that are themselves based on transconductors that can be realised by both continuous time and switched capacitor circuit techniques. Factors considered are the sensitivity of the filter response to variations in component parameters and the need to apply nodal voltage scaling to the amplifier output voltages to maximise signal handling capability. A formulation of filter structure in terms of transconductor interconnection provides a generalised framework within which to classify alternative realisations. Examples of polynomial and elliptic switched capacitor filters are given