Design and Analysis of Resonant-Tunneling-Diode (RTD) Based High Performance Memory System

Tetsuya UEMURA  Pinaki MAZUMDER  

IEICE TRANSACTIONS on Electronics   Vol.E82-C   No.9   pp.1630-1637
Publication Date: 1999/09/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Integrated Electronics and New System Paradigms)
Category: Application of Resonant Tunneling Devices
resonant tunneling diode,  DRAM,  sense amplifier,  instability,  refresh-free,  

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A resonant-tunneling-diode (RTD) based sense amplifier circuit design has been proposed for the first time to envision a very high-speed and low-power memory system that also includes refresh-free, compact RTD-based memory cells. By combining RTDs with n-type transistors of conventional complementary metal oxide semiconductor (CMOS) devices, a new quantum MOS (Q-MOS) family of logic circuits, having very low power-delay product and good noise immunity, has recently been developed. This paper introduces the design and analysis of a new QMOS sense amplifier circuit, consisting of a pair of RTDs as pull-up loads in conjunction with n-type pull-down transistors. The proposed QMOS sensing circuit exhibits nearly 20% faster sensing time in comparison to the conventional design of a CMOS sense amplifier. The stability analysis done using phase-plot diagram reveals that the pair of back-to-back connected static QMOS inverters, which forms the core of the sense amplifier, has meta-stable and unstable states which are closely related to the I-V characteristics of the RTDs. The paper also analyzes in details the refresh-free memory cell design, known as tunneling static random access memory (TSRAM). The innovative cell design adds a stack of two RTDs to the conventional one-transistor dynamic RAM (DRAM) cell and thereby the cell can indefinitely hold its charge level without any further periodic refreshing. The analysis indicates that the TSRAM cell can achieve about two orders of magnitude lower stand-by power than a conventional DRAM cell. The paper demonstrates that RTD-based circuits hold high promises and are likely to be the key candidates for the future high-density, high-performance and low-power memory systems.