Black Box Modelling at the Circuit level: Op-Amp as a Case Study

In general, models at the device and circuit levels are very important in system design. Building compact models at the circuit level is complicated, needs a lot of physical information about the circuit and moreover it has a long simulation time. We present in this paper an alternative modeling methodology, black box modeling. In this technique, we need only the output behavior of the circuit. We get this behavior either from measurements or simulations from previously built compact models. We apply this technique to the operational amplifier as a case study. We use the opamp design consisting of BSIM3v3-based compact transistor models to obtain the performance of the circuit. An excellent agreement is obtained between the output current from the black box model of the op-amp and the corresponding output from the model used to build it