Design of Universal Active Filter

A universal active filter is designed to solve the disadvantages of excessive components,bulk size,complex debugging,cumbersome design and bad filtering,which are all the characteristics of a conventional active filter.The function of filtering can be achieved through filter chip MAX275.The digital potentiometer is controlled by single chip microcomputer(MCU)to obtain accurate parameter values of external components which are set by keyboard and displayed by LCD.Data from tests show that the functions of low-pass and band-pass filtering of the second order,the fourth order,the sixth order and the eighth order can be achieved in the design.The universal filter improves efficiency with high cost-performance ratio and practical value.