OPEN FAULTS IN BICMOS GATES

Opens in BICMOS structures are analyzed here. It is shown that some op ens cannot be detected by stuck-fault or other functional tests, since some transistors in BiCMOS gates do not affect the logical function o f the gate. A switch-level model for CMOS circuits is extended to incl ude bipolar devices. With this switch-level model, opens that cannot b e detected by stuck-faults or other functional tests are easily identi fied. It is also shown that, in BICMOS circuits, an open defect in one transistor can accelerate the wearout of another nondefective transis tor.