Behavioural modelling of operational amplifier faults using VHDL-AMS

The use of behavioural modelling for operational amplifiers has been well known for many years and previous work has included modelling of specific fault conditions using a macro-model. In this paper, the models are implemented in a more abstract form using an Analogue Hardware Description Language (AHDL), VHDL-AMS, taking advantage of the ability to control the behaviour of the model using high-level fault condition states. The implementation method allows a range of fault conditions to be integrated without switching to a completely new model. The various transistor faults are categorised, and used to characterise the behaviour of the HDL models. Simulations compare the accuracy and speed of the transistor and behavioural level models under a set of representative fault conditions