The Positive Impedance Converter

EE 54 October 1987 THE POSITIVE IMPEDANCE CONVERTER by A.B. Bradshaw One of the very practical means of simulating inductance in electrical circuits is by the use of gyrators. The positive im- pedance converter is a member of this family. Its main use is to replace wound inductors in AF circuits, particularly where these have large values, or to simulate coils at very low frequencies. The positive impedance con- verter makes use of operational amplifiers: two are needed to simulate a grounded inductor; four are required to simulate a balanced inductor. But only four opamps are needed to simulate a node, containing balanced and grounded induc- tors, as will be shown later. Where simulation of grounded inductors is used, the opamps should be operated from balanced power supplies. The writer has used the PIC as a circuit element for a number of years in the design of high- performance AF filters. The Q values obtained with these devices is very much higher than that of the wound equi...