RC active filters for the D3 channel bank

The development of the voice-frequency active filters for the D3 channel bank is described. These filters are the first single-substrate RC active filters using thin-film tantalum RC and silicon integrated-circuit technology to be produced on a large scale by Western Electric. To create complete confidence in both the design and the new technology, an extensive model building and testing program was undertaken. In addition, continuous interaction with manufacturing engineers resulted in a design that facilitated the introduction of this new technology in a large-scale manufacturing environment. Significant advances were made in reducing the complexity of tuning active filters. In fact, the tuning and testing procedure has been adapted for use with a totally automated computer-controlled test set. Furthermore, a Monte Carlo statistical simulation of the manufacturing process of the filters was developed. This model includes tolerances of the manufactured components, test set errors in measuring gain and component values, resistor adjustment accuracies, and temperature and aging behavior of the components. This computer program has been an invaluable tool in determining the requirements for tuning, testing, and optimizing the final design for minimum manufacturing cost.