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

Abstract

A method of designing continuous-time active <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> filters which employ only capacitors and FET transistors is presented. The effective <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> time constants of these filters are determined by capacitor ratios. The filters employ switched resistors. These filters can use any existing active <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> or passive <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> 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.