Tunable filter network having dc accuracy

Abstract

A highly DC accurate filter network capable of implementing a transfer function of arbitrary complexity is disclosed herein. The filter network includes a differential integration and summation network having a first input port connected to an input terminal of the filter network, a second input port, and an output port. A filter circuit having a predefined transfer function is connected between the output port and an output terminal of the filter network. In addition, a feedback path connects the output terminal to the second input port of the differential integration and summation network. During operation of the filter network the filter circuit cooperates with the differential integration and summation network so as not to affect the amplitude of the DC component of an input signal applied to the input terminal. This results in high DC accuracy even if the filter circuit is implemented using, for example, active components. Moreover, the overall transfer characteristic of the filter remains highly DC accurate even when filter circuits having adjustable transfer characteristics, such as clock-tunable switched capacitor filters, are incorporated therein.