A Comprehensive Fault Macromodel For Opamps

In this paper, a comprehensive macromodel for transistor level faults in an operational amplifier is developed. With the observation that faulty behavior at output may result from interfacing error in addition to the faulty component, parameters associated with input and output characteristics are incorporated. Test generation and fault classification are addressed for stand-alone opamps. A high fault coverage is achieved by a proposed testing strategy. Transistor level short/bridging faults are analyzed and classified into catastrophic faults and parametric faults. Based on the macromodels for parametric faults, faults simulation is performed for an active filter. We found many parametric faults in the active filter cannot be detected by traditional functional testing. A DFT scheme alone with a current testing strategy to improve fault coverage is proposed.