Switched-resistor filters-A continuous time approach to monolithic MOS filter design

A method of designing continuous-time active filters which employ only capacitors and FET transistors is presented. The effective time constants of these filters are determined by capacitor ratios. The filters employ switched resistors. These filters can use any existing active or passive topology as the basis for the design and inherit the sensitivity properties of the circuit from which they are derived. These switched-resistor (SR) filters operate over a wide frequency range and are manufacturable in monolithic form using a basic MOS process which requires no component trimming.