The Analysis And Design Based On 65nm SRAM For Low Power Consumption Current Mode Sense Amplifier

Recently, SRAM has played more and more important role in memory circuit. And design of sense amplifier (SA) has significant influence on SRAM because the SA could detect small signal difference and amplify it quickly and precisely, providing considerable performance promoting for SRAM. For these reasons, SA has been extensively used in various kinds of circuits.With the increasing development of technology, the structure of SA is slightly different, but generally can be divided into two categories:voltage mode sense amplifier and current mode sense amplifier. Voltage mode sense amplifier depends on detecting small differential voltage on the bit line and amplify it to a full swing signal while current mode sense amplifier senses differential current and enlarge it to the CMOS level. Voltage mode sense amplifier has simple structure and good stability, but for the load capacitance of the bit line it can not reach high speed. Current mode sense amplifier could achieve high speed because current differece appeares quickly, but on the other side it also has large power consumption and poor stability. Design of sense amplifier should consider many metrics, such as speed, power consumption, area and yield, these metrics influence each other. With the development of process, the power voltage has been lower and lower, two factors, speed and power consumption will become more important.Based on the requirements aboved, this thesis first analyzes the key points and difficulties in the design of sense amplifier, then introduces several structures of commonly used sense amplifiers and explains the advantages and disadvantages of them. Finally proposes a new type of current sense amplifier with low power consumption. This SA removes DC pathway beside the discharging time to reduce the consumption. Simulation results with 65nm in spectre of cadence shows that compared with the WTA sense amplifier under three kinds of corners:TT、SS、FF. the speed of the new SA has improved 40%.38% and 31%. and the power consumption of the new SA has reduced 64%.88%and 68%.In addition, this thesis proposes two available improvement solutions for the new type current mode sense amplifier:input self-conpensation circuit and anti threshold voltage fluctuations circuit. They are proposed to solve the instable factors in circuit and the undesirable impact with them. By using these solutions, we can prevent the occurrence of functional failure and improve the accuracy of the amplifier effectively.