Design of Tunable Polyphase Filter Using MOSFET

A conventional polyphase filter which comprises of passive components such as capacitors and resistors consumes large chip area. Rapid advancement of complementary metal oxide semiconductor (CMOS) technology brings unparallel advantage in the respect of chip area consumption. In this work, the characteristics of the metal-oxide-semiconductor-field-effect transistor (MOSFET) have been investigated to replace passive components in polyphase filter in order to reduce the area of polyphase filter. Implementation of tunable polyphase filter by using MOSFET is proposed. Nonetheless, using active device as the replacement of passive components cause the new problems such as non-linearity and parasitic effects. These problems introduce higher gain and phase error of the polyphase filter which degrades mirror image suppression. Finally, ways to suppress the errors have been discussed.