A new CFA frequency model including load-dependent instabilities

The current-feedback operational amplifier (CFA) is an active device which uses the supply-current sensing technique in order to achieve high performance features for analog signal processing applications. However, under certain load conditions, the CFA exhibits an unstable behavior. This work presents a new frequency model which rakes into account the non-unilateral characteristics of the CFA buffer stages and includes the load-dependent instabilities. The model can be easily incorporated into a standard macromodel for simulation purposes or used analytically for accurate circuit design based on CFAs. As a consequence of this approach, some improvements in the CFA structure could be suggested.