A Bubble Memory Differential Detector

In typical field-accessed magnetic bubble memories (MBM), stored binary data on memory chips are detected by processing millivolt-level signals that are measured differentially across a matched pair of permalloy magnetoresistive sensor strips. 13 Ideally these sensors are subjected to the same magnetic, electrical, and environmental conditions with the exception that only one, the active sensor, is subjected to H fields of traversing bubble domains. In the drive field period of a field-accessed MBM chip, by design at least one time interval exists, defined here as the detection interval (DI), in which the sensor differential response is relatively free of unavoidable signal interferences such as MBM function drive crosstalk and sensor magnetoresistive switching noise. Within the DI a detectable difference should exist between responses for the bubble and no-bubble cycles of the memory. Even after carefully choosing the DI, undesirable sensor response variations can still occur. Variations within the DI that have been of major concern in the use of previous nonadaptive MBM detectors are 485