对寄生电容不灵敏的开关电容有源滤波器的设计

采用单位缓冲器设计对寄生电容不灵敏的开关电容(SC)频率相关负电阻(FDNR)元件，利用该元件对椭圆函数式LC低通滤波器进行SC模拟。为了获得电容最佳值，提出了一种简单的最优化方法；并采用寄生电阻预畸变与SC负电阻相结合的办法，设计的SC滤波器对寄生电容不灵敏，且电路简单。在电子工作平台(EWB)上进行五阶椭圆低通SC-FDNR滤波器仿真，测量数据最大相对误差为0．948％，仿真结果表明该方法实用可行，效果明显。

Designing Switched-Capacitor Active Filters Insensitive to Parasitic Capacitance

An unit buffer is adopted to design frequency dependence negative resistance(FDNR) element of switched-capacitor(SC) which is insensitive to parasitic capacitance. SC uses the element to simulate LC low pass filter of ellipse function. This paper presents a simple optimization method to get the best value of the capacitance. The SC filter is insensitive to parasitic capacitance implemented by a simple circuit in the way of combining advance mutation of parasitic resistance and SC negative resistance. A five-order ellipse low pass SC-FDNR filter is simulated by Electronics Workbench. Greatest relative error of the measured data are 0.0948%. Simulation results indicate that the method is practical and efficient highly.