Design considerations for a high performance OTA with fully differential gain enhancement

Abstract

A small-signal analysis of the basic active cascode gain-enhancement circuit is presented. The analysis results in a three-pole one-zero representation. It shows that although OTA's DC gain is boosted, its frequency response becomes worse because of two factors: a doublet and the lower nondominant pole. An effective compensation method is then introduced to reduce this effect. Based on the above results, the design of a high-performance OTA is presented which uses a fully differential gain-enhancement technique. This improves the settling behavior and reduces power and area.