A 2.5D Ferrite Memory Sense Amplifier

Abstract

In recent years, large-core memories have been developed that use two-wire arrays and are operated in a mode colloquially called 2.5D. The intrinsic noise problem in a 2.5D ferrite memory system is quite severe because the core signals must be sensed off an array line which is also conducting a half-select drive current. The resulting large pedestal and delta noise components, which are generated during the read cycle, severely limit the memory performance. While the delta noise can be strobed out of the sense amplifier, the pedestal noise must be eliminated by circuit techniques. To handle this noise problem, a delay and difference amplification technique is used that permits a short recovery from the pedestal noise and a corresponding increase in memory speed. The implementation of this circuit function is shown, in the final analysis, to be a relatively simple filter used in conjunction with a conventional difference amplifier and detector.