摘要
讨论了由低阶有源滤波器实现高阶有源滤波器的理论证明，并经多次验算，给出了三阶有源滤波器元件参数的选择方案。对由一阶和二阶低通滤波器组成的三阶低通滤波器进行证明，论证它是否能满足三队巴特沃斯（Butterworth）低通滤波器的条件，根据实践经验，给出实用电路，测量出有关数据，同时给出实验证明。
How to obtain the thind - orter filter wity the low - order filter is the main concem of the paper. Butterworth approxination and constraints that the third - order low - pass filter needs provide the theoretical basis for the feasibility of the design of third - order filter. A nmber of tests offer the scheme to get the parameters of the components of the filter and show that the filter is efficient.
