When we want to control a very fast system, like an operational amplifier, we have the problem that the controller must be faster than the system. The controloller’s work conditions are extreme and it is very difficult to find an optimal and implement solution. The QFT design methodology allows to look for real solutions to the problem. To desmostrate this afirmation, a study has been done about the operational amplifier (O.A.)LM12CL ofNational Semiconductor. The result is a robust controller that allows its operation in extreme conditions.