LC SIMULATION BY ACTIVE RC LOW-PASS FILTER WITH REDUCED NUMBER OF OPERATIONAL AMPLIFIERS.

An active RC filter which simulates an LC ladder filter is known to be of lower sensitivity than a cascade filter. A number of filters of this type have been proposed in recent years. This paper describes a synthesis method for LC simulation by an active RC low-pass filter with reduced number of operational amplifiers by using a Sallen-Key circuit for the 2nd-order circuit encountered in the conventional leapfrog composition and by eliminating some of the variables of the input and output sides. We discuss a sign decision method for the node voltage and loop current of a prototype LC filter and the elimination of variables. We derive relations for the variables which should be realized in the circuit and introduce a circuit which can realize them.