CMOS low-VT preamplifier for 0.5-V gigabit-DRAM arrays

Abstract

A novel CMOS low-VT preamplifier suitable for low-voltage and high-speed mid-point sensing was developed for gigabit DRAM. This preamplifier consists of a low-VT NMOS cross couple, a low-VT PMOS cross couple and a high-VT CMOS latch. The sensing speed of the proposed preamplifier at dataline voltage of 0.5 V is 62% higher than that of a conventional preamplifier. By activating the low-VT NMOS and PMOS cross couples temporarily during write operation, writing time is 72% shorter compared to the case with the high-VT CMOS latch only. Data-line charging current of a memory cell array with the proposed preamplifier is reduced by 26% by decreasing dataline voltage from 0.8 to 0.5V.