Design and Stability Analysis of 6T and 7T SRAM cells

Random Access Memory (RAM) is a critical component of modern computing systems. RAM allows the Central Processing Unit (CPU) of a computer to temporarily store data in such a way that it is immediately available to the processor. This drastically decreases computing time as well as increases program performance, as the CPU has the information it requires immediately and does not have to access the hard drive, a very time-consuming process. All RAM is volatile, meaning it loses all information stored when it loses power. Static Random-Access Memory, termed SRAM for short, is a critical component of modern computing systems. While many people are familiar with Dynamic RAM, the infamous sticks that all modern computers require, many don't realize the critical role the S variant plays. SRAM is found in almost all modern computing systems that have a user interface, being found in devices as simple as a children's toy to systems as complex as a driverless car. Many SRAM designs have been constructed over the years, however the 6Transistor (6T) and 7Transistor (7T) variants have prevailed as the most popular designs, due to them being constructed purely out of CMOS Transistors. The stability of these memory components are analyzed using Static Noise Margin (SNM). The 7T historically has a larger margin than the 6T in both categories, as it possesses an additional transistor that controls the read and write process. However, with SNM graphs, its observed that while the 7T cell holds an advantage, it appears to be decreasing at an ever faster rate the smaller it becomes. As consumer demand for smaller and more powerful devices grows, this research aims to compare the stability of 6T or 7T architectures for long term use in consumer electronic devices.