Active filter circuit using RC elements and operational amplifiers - uses min. number of components of wide tolerance values connected as four terminal network

摘要

A filter circuit built up of ohmic resistances, condensers, and operational amplifiers in the form of a four terminal network. It is designed to have max. tolerance in component values and min. number of circuit elements. It has only two operational amplifiers. The input and output each have one earthed terminal. There is a resistor (R1) and a capacitor (C2) in series with an operational amplifier (A1) in the long arm. They are bridged by a second operational amplifier (A2) and resistance (R21) in series with a capacitor (C12) between the junction points of (R1/C2) and (A2/R21). One input of each operational amplifier is taken to earth.