Research On Offset Voltage Reduction Technology Of Static Random Access Memory Sense Amplifier

In the environment of rapid development of technology,mobile terminals and smart homes have become popular in people's lives.In order to meet the requirements of artificial intelligence for hardware facilities,process nodes are continuously updated,and transistors integrated in wafers of the same area also show an exponential growth.As the fastest storage device,SRAM has gradually increased its proportion in the SoC.As the SRAM capacity increases,it is also affected by the transistor threshold voltage mismatch.In order to effectively reduce the offset voltage of the sense amplifier,an offset voltage suppressed sense amplifier with self-adaptive distribution transformation technique is proposed to accelerate the reading speed of SRAM and reduce energy consumption.The main works of this paper are listed as follow:Firstly,we introduced the overall architecture of SRAM,and analyzed the three working states of reading,writing and holding.The reading operation is the timing critical path of SRAM.Then,we introduced that the sense amplifier can speed up the time of read operation effectively.The sense amplifier can be divided into two types,which are:voltage mode sense amplifier and current mode sense amplifie.Voltage mode sense amplifier has relatively simple circuit structure,stable and efficient performance,but it needs certain differential voltage as input.Therefore it is strongly influenced by bit-line load capacitance;Current mode sense amplifier input bit line current,its speed is fast.It will not be affected by the bit-line load capacitance.But the circuit structure of the current mode sense amplifier is complex.And the process fluctuations affect its stability seriously.The advantages of three common sense amplifiers are compared and analyzed in this paper.The simulation results show that the traditional coupled latched-type sense amplifiers have better ability to suppress the process fluctuation.Secondly,we analyzed the principle of some different sense amplifiers and introduced several calibration ideas to reduce the offset voltage through different ways.Then this paper introduced the circuit principle and working mode of various schemes in detail.Through the simulation and verification of the offset voltage improvement effects of various designs,we analyzed their advantages and disadvantages.Finally,this paper proposed an offset voltage suppressed sense amplifier with self-adaptive distribution transformation technique.We analyzed the circuit structure,theoretical derivation and working principle in detail.Under the condition of adding a small number of peripheral circuits,the difference of the current of transistor is reduced by controlling the voltage of NMOS gate.The offset voltage is effectively reduced by 57.1%(under the TT process angle),and the effect of the offset voltage suppressed sense amplifier with self-adaptive distribution transformation technique is verified by simulation at different process angles and temperatures.Monte Carlo simulation results show that the offset voltage improvement effect is 49.9%-58.3%.