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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。
Based on the 0.18-μm 1.8V CMOS standard process, a high precision switched-current memory cell is designed. By setting the memory transistor to work in the linear region, combined with the virtual switch technology to reduce the threshold voltage mismatch and clock feedthrough generated by the harmonic distortion, effectively eliminating the gain error and drift error. Use Specter simulator to verify the layout. The error is only 0.5% when the input signal frequency is 200kHz, the amplitude is 5μA and the sampling frequency is 5MHz. The error is still less than 1% when the input signal amplitude is as low as 1μA. The simulation results show that the circuit has high precision and can be used as the basic module of the filter, Σ-Δ modulator system.