A Categorical Review on First Order Universal Filters

This paper highlights the notable individual contributions of the researchers in the field of first-order universal filters, and additionally, segregates the reviewed works amongst various scientifically chosen categories. Relevant first-order universal filter circuits reported in the last two decades are chosen for the review. The segregation categories are based on the well-recognized signal processing features, such as the mode of operation, number of active and passive elements, grounded nature of the passive components, simultaneous availability of the outputs, and the provision for resistorless realization. These works are also analyzed for various other performance enhancing attributes, like support for cascadability, transistor count, load insensitivity, matching constraints, etc. Moreover, exhaustive observations regarding existing works are also included individually in tabular form to mainly emphasize newness, uniqueness and downsides of reported ideas, which further enrich the quality of the review paper.