CMOS ACTIVE-FILTER DESIGN AT VERY HIGH-FREQUENCIES

A study of the limitations of active CMOS filters at high frequencies suggests automatic means to compensate imperfections in the filter response introduced by active devices. The effects of nonzero FET output conductance, limited frequency response and noise on the filter characteristics, and dynamic range have been analyzed, particularly for filters with high Q components, and simple equivalent circuits have been developed to describe them. These ideas have been used to demonstrate a 3-μm CMOS realization of a fourth-order bandpass filter with a 250-kHz passband centered at 12.5 MHz. © 1990 IEEE