On unstable operational amplifiers

In this paper possible reasons for instability of operational amplifiers with internal frequency compensation are discussed and a simplified analysis is performed which reveals the possibility of instability (that means a negative time constant or a dominant pole in the right half of the p-plane). The existence of unstable operational amplifiers is verified with time domain and other experiments. Measurement methods, also working in the time domain, are discussed which allow the determination of interesting data for stable as well as unstable operational amplifiers. Furthermore, the consequences of the instability of operational amplifiers in the field of active network synthesis are studied.