Switched-capacitor notch filter with programmable notch width and depth

Abstract

A notch filter circuit includes first and second operational amplifiers, each having a capacitor connected from the amplifier output to the input. A third capacitor is connected between the second-amplifier input and the filter circuit input. A first switched-capacitor resistor is connected between the filter circuit input and the first-amplifier input. A second switched-capacitor resistor is connected between the first amplifier output and the second amplifier input. The second-amplifier output is connected to the filter circuit output. A third switched-capacitor resistor is connected between said filter circuit output and said first amplifier input; First and second programmable capacitor arrays are connected respectively in parallel with the third switched-capacitor resistor and in parallel with the first switched-capacitor resistor, so that a change only in the capacitance of the second capacitor array causes a corresponding change in the filter notch depth and a change only in the capacitance of the first capacitor array causes a corresponding change in the filter notch width. The first and second capacitor arrays each have a group of digital programming terminals that may be connected together for making fixed the ratio of the capacitance values of the two arrays. A digitally programmable voltage divider circuit connected in series with the second programmable capacitor array permits the independent programing of notch depth, i.e. without affecting notch width.

Dependencies are inferred from the claim text.