Functional Tantalum Thin-Film Resistive Networks and Decoders

Over the past several years related design procedures have been devised whereby various resistance network functions normally achieved by a network of several discrete resistors are now obtained from functional resistive "circuits." The realization results in novel structures which include conducting tabs placed on the perimeter of a geometrically shaped resistive film. Several resistance functions (attenuation and D-A decoding functions) can be provided simultaneously by using a single two-dimensional resistive film and a multiplicity of conducting tabs placed on its perimeter. Integrated resistive film networks offer several advantages over their lumped element equivalents. These include fewer interconnections, simple photolithography, built-in redundancy, and more uniform power dissipation. These advantages result in higher reliability, lower cost, and a more efficient use of the substrate area. When realized as tantalum integrated circuits, functional resistive networks offer high stability, high initial precision, low noise, resistance tracking, and small temperature coefficient of resistance.