高精度开关电流存储单元的设计

Design of High Accuracy Switched-Current Memory Cell

基于0.18-μm 1.8VCMOS标准工艺,设计了一个高精度开关电流存储单元。通过设置存储晶体管工作于线性区,并结合虚拟开关等技术,降低了由阈值电压失配和时钟馈通所产生的谐波失真,有效消除了增益误差和漂移误差。利用Spectre仿真器,对版图进行后仿真验证。当输入信号频率为200kHz、幅度为5μA、采样频率为5MHz时,误差仅为0.5%,输入信号幅度低至1μA时,误差依然低于1%。仿真结果表明,电路具有高精度,可作为滤波器、Σ-Δ调制器等系统的基本模块。

A switched-current memory cell with high accuracy was designed based on 0.18-μm 1.8 V CMOS standard technology.By setting up memory transistor in linear area and using virtual switch,harmonic distortions due to threshold voltage mismatch and clock feedthrough was reduced,and gain and offset errors were eliminated effectively.Post simulation with Cadence＇s Spectre showed that the circuit had an error of only 0.5% for 200 kHz input signal with an amplitude of 5 μA and a sampling frequency of 5 MHz.Simulation results indicated that the memory cell had high accuracy and could be used as basic block of filter and delta-sigma modulators.