Design of 64-bit SRAM using single electron transistor
Kale, Vishwamber N.
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The present day devices demand memory chips with larger size and smallphysical dimensions. This drives the designer to design high density memorydevices. The memory designed using CMOS technology do not have comparablespeed to match with the speed at which processor operate. Hence, we aretargeting to design high speed SRAM using Single Electron Transistor (SET). SETconsumes ultra low power. SET circuits can be stacked above the CMOS platform.The basic components of SRAM are decoder, sense amplifier, control block,write circuit driver and 6-T SRAM cell. To design stable SRAM, proper sizingof each transistor is reqiured. Decoder selects memory address for reading andwriting data. So proper designing of decoder is required. Due to high capcitanceof word line, Bitline doesnt get full voltage swing. Therefore, SRAM needs to bedesigned with higher stability. Selection of sense amplifier depends on the rateof bit-line discharging. To generate internal signals within SRAM for performingread and write operations designing a controller circuit is required.To achieve above mentioned specifications, stability of SRAM is verified usingN-Curve. Stability comparison is performed for both CMOS and SET basedSRAM. Dynamic decoders are used in SRAM, as they outperform conventionaldecoder in terms of power and delay. Comparison between SET and CMOS baseddecoder and sense amplifier is performed in terms of power and delay. Controllerdesign for generating internal signal for read and write operation is implementedfor both CMOS and SET based SRAM.We have verified the functionality of 64-bitSRAM by simulating read and write operations for SET and 45nm CMOS technology.Access time for SET based SRAM is 121 ps and for CMOS based SRAMis 872 ps. SET based SRAM takes total power as 723 nW and CMOS based takestotal power as 956 mW. In this work, we present SET based SRAM which is fasterand ultralow-power as compared to the 45nm CMOS based SRAM.
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